THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

LOS  ANGELES 

GIFT  OF 
John  S.  Prell 


COMPRESSED  AIR 

Its  Production,  Uses,  and  Applications 


COMPRISING 

THE    PHYSICAL    PROPERTIES    OF    AIR    FROM    A    VACUUM 

TO    ITS    LIQUID     STATE,    ITS    THERMODYNAMICS, 

COMPRESSION,  TRANSMISSION    AND    USES 

AS  A 

MOTIVE    POWER 

In  the  Operation  of   Stationary  and   Portable    Maciiinery,    in   Mining,    Air    Tools, 
Air  Lifts,  Pumping  of  Water,  Acids,  and  Oils ;  the  Air  Blast  for  Cleaning 
and  Painting,  the    Sand    Blast    and  its  Work,  and   the    Numerous 
Appliances    in    which    Compressed    Air   is    a    Most    Con- 
venient and  Economical  Transmitter  of  Power  for 
Mechanical  Work,  Railway  Propulsion,   Re- 
frigeration   and    the    Various    Uses 
to  which   Compressed 
Air  has  been 
Applied. 

¥ 
WITH  FORTY  AIR  TABLES  AND  FIVE   HUNDRED  AND  FORTY-FIVE  ILLUSTRATIONS 


By  GARDNER    D.  HISCOX,  M.E. 

'Mechanical  Movements,  Powers,  Devices  and  Appliances,"  "Gas,  GasoH 
Oil  EngiPe^^"^wiriys  Vd|^es,  A^^imJ^^^  gtc.^tc. 

Civil  <&  Mechanical  Engineer. 


SAN  FKAiN CISCO,  CAL. 

NEW    YORK  ' 

MUNN    &    COMPANY 

OFFICE    OF    THE    SCIENTIFIC    AMERICAN 

361  Broadway 

1901 


Copyright,  1901, 
By   NORMAN   W.    HENLEY  &   CO. 


COMPOSITION    AND    PRINTING    BY 

THE     PUBLISHERS'     PRINTING     COMPANY, 

NEW    YORK,    N.    Y., 

U.    S.  A. 


PREFACE. 


THE  literature  on  the  commercial  uses  of  compressed  air, 
especially  in  its  application  to  the  mechanic  arts,  has  not 
kept  pace  with  the  growing  importance  of  the  subject,  having 
been  confined,  in  the  main,  to  occasional  papers  presented  to 
engineering  societies,  and  to  special  articles  appearing  at  inter- 
vals in  the  various  technical  journals  of  this  and  foreign  coun- 
tries, or  in  the  still  more  fugitive  form  of  trade  circulars;  but 
even  these,  fragmentary  publications  at  best,  cover  scarcely 
more  than  the  past  two  decades. 

The  thermodynamic  treatment  of  air  under  compression,  its 
transmission  and  expansion,  have  been  ably  worked  out  by  care- 
ful experimenters  and  communicated  to  scientific  societies  by 
competent  writers ;  these  articles,  valuable  in  themselves,  have 
not  met  the  requirements  of  the  modern  engineer,  whose  imme- 
diate necessities  demand  a  more  complete  gathering  of  the 
widely  distributed  data  relating  to  this  subject,  as  well  as  a  better 
classification  of  the  known  properties  of  the  atmosphere.  This 
want  has  long  been  apparent  to  the  author  by  reason  of  many 
years'  experience  in  answering  constantly  recurring  inquiries 
relating  to  compressed  air,  and  to  its  direct  application  to  the 
commercial  needs  of  the  day.  The  fund  of  information  ac- 
quired and  carefully  preserved  by  the  author  during  the  many 
years  of  his  editorial  work  is  now  brought  into  compact  form 

\^     and  in  a  single  volume  for  ready  reference.     That  this  has  been 
no  light  task  v/ill  be  apparent  from  even  a  casual  perusal  of  the 

^-^    present  work. 

X  The  progressive  advancement  in  experimental  research  ex- 


X 


^ 


713457 


8  PREFACE. 

tends  in  two  opposite  directions :  the  partial  vacuum  incident  to 
the  ordinary  operations  of  an  air  pump  or  the  condensation  of 
watery  vapor  has  been  extended  by  other  methods  to  the 
highly  attenuated  results  obtained  in  the  manufacture  of  incan- 
descent lamps;  while,  on  the  other  hand,  compression  has  ex- 
tended through  its  various  stages  until,  and  in  connection  with 
a  very  low  temperature,  the  final  product,  liquid  air,  has  been 
made  commercially  available.  Many  of  the  difficulties  in  regard 
to  the  expression  of  mathematical  details  and  thermodynamic 
formulas  have  arisen  in  consequence  of  this  progressive  ad- 
vancement ;  so  also,  the  knowledge  of  the  atmospheric  relation 
to  other  elements  is  yet  in  a  progressive  state ;  the  practical  ap- 
plication of  compressed  air  for  doing  mechanical  work  is  of  so 
recent  date  that  the  design  and  construction  of  any  of  the  most 
useful  machines  operated  by  compressed  air  rest  upon  empirical 
rather  than  scientific  formulas.  It  is  one  of  the  objects  of  the 
present  volume  to  make  available  the  ascertained  facts  of  ex- 
perimental research  in  atmospheric  phenomena,  and,  so  far  as 
possible,  the  fundamental  basis  upon  which  such  ascertained 
facts  securely  rest. 

To  limit  the  consideration  of  the  properties  of  air  when  sim- 
ply compressed  above  the  ordinary  pressure  of  the  atmosphere 
was  believed  to  be  wanting  in  scope  to  make  the  treatment  of 
the  subject  complete ;  this  work  includes,  therefore,  a  consider- 
ation of  the  properties  of  air  below  atmospheric  pressure,  for 
the  reason  that  we  are  surrounded  by  an  atmosphere  compressed 
by  gravity,  but  it  is  used  in  the  arts  in  many  ways  much  below 
atmospheric  pressure,  even  approaching  the  zero  condition  of  a 
vacuum,  so  that,  remote  as  the  connection  appears,  this  subject 
of  partial  pressures  below  the  atmosphere  properly  belongs  to 
a  treatise  on  compressed  air. 

The  wide  range  of  manufacturing  interests  in  which  com- 
pressed air  plays  an  important  or  even  a  subordinate  part  is 
such  that  special  machines  for  its  production  and  utilization 
areas  numerous  as  the  diversified  industries  of  our  dav;  this 


TREFACE.  9 

condition  has  suggested  the  large  number  of  illustrations  em- 
ployed to  place  before  the  reader  the  salient  features  of  only 
the  latest  and  best  designs.  These  designs  include  portable 
machines,  together  with  a  large  number  of  individual  and  spe- 
cial tools  designed  for  and  greatly  contributing  to  the  lessening 
of  manual  labor,  as  ^Yell  as  tending  to  increase  the  output  of 
useful  work. 

The  development  of  the  caisson  method  in  submarine  work 
for  engineering  structures  has  become  very  general ;  requiring 
not  only  special  appliances,  but  introducing  problems  in  hygiene 
which  do  not  ordinarily  occur  in  engineering  practice ;  the  sen- 
sations and  phy.sical  effect  of  varying  air  pressures  and  temper- 
atures upon  workmen  engaged  in  labor  of  this  kind  belong  es- 
sentially to  the  subject-matter  of  this  work,  and  have  been 
included. 

Within  the  past  few  years  an  important  and  useful  com- 
mercial effect  has  been  obtained  by  the  use  of  compressed  air 
and  its  subsequent  expansion  in  the  production  of  temperatures 
suited  to  refrigerating  purposes ;  such  machines  are  in  use  on 
warships  and  other  vessels  in  which,  for  one  reason  or  another, 
the  use  of  ammonia  gas  is  either  objectionable  or  prohibitive. 

The  author,  recognizing  the  economic  value  of  such  ma- 
chines, has  given  considerable  space  to  the  consideration  of  the 
physical  and  thermodynamic  problems  connected  therewith. 
There  are  many  interesting  problems  in  this  connection  which 
lie  beyond  the  domain  of  commercial  refrigeration,  in  which, 
by  the  production  of  temperatures  far  below  the  Fahrenheit 
zero  and  approaching  the  absolute  zero,  the  critical  temperature 
of  air  is  passed  and  its  physical  condition  changed  from  a  gase- 
ous to  a  liquid,  and  thence  to  a  solid  state;  as  this  subject  has 
been  fully  treated  in  a  recent  volume  on  Liquid  Air,  it  has 
therefore  been  given  but  limited  space  in  this  work. 

Among  the  available  sources  of  information  employed  by  the 
writer  have  been  the  various  standard  treatises  on  thermody- 
namics, including  Weisbach,  Rankine,  Roentgen  and    Dubois, 


lO  PREFACE. 

Thurston,  De  Volson,  Wood,  and  others ;  free  use  has  been  made 
of  articles  on  compressed  air  and  its  appliances  which  have  ap- 
peared in  the  Scientific  American  from  time  to  time  ;  acknowledg- 
ment is  also  due  to  the  leading  technical  journals  of  this 
country  and  of  Europe ;  while  the  writer  would  be  wanting  in 
appreciation  and  gratitude  if  he  failed  to  suitably  acknowledge 
the  action  of  his  friend  Mr.  William  L.  Saunders,  editor  and 
proprietor  of  the  journal  Compressed  Air,  who,  with  charac- 
teristic liberality,  tendered  the  entire  valuable  contents  and 
illustrations  of  this  journal  to  the  use  of  the  author  in  the  prep- 
aration of  this  volume.  Gardner  D.  Hiscox. 

New  York,  November,  iqoi. 


CONTENTS. 


CHAPTER  I.  PAGE 

Historical, 13 

CHAPTER  n. 
Physical  Properties  of  Air,     ..........     29 

CHAPTER  HI. 
Air  in  Motion  and  its  Force,  .........     41 

CHAPTER  IV. 
Air  Pressures  Below  Atmospheric  Pressure,       ......     49 

CHAPTER  V. 

The  Flow  of  Air  under  Pressure  from  Orifices  into  the  Atmosphere,     89 

CHAPTER  VI. 
The  Power  of  the  Wind, 97 

CHAPTER  VII. 
Isothermal  Compression  and  Expansion  of  Air,  .        .        .        .        .        .113 

CHAPTER  VIII. 
Thermodynamics,         .         .         .         .         . .119 

CHAPTER  IX. 
Adiabatic  Compression  and  Expansion 133 

CHAPTER  X. 
The  Compressed-Air  Indicator  Card, 153 

CHAPTER  XI. 
Actual  Work  of  the  Compressor, 163 

CHAPTER  XII. 
Multi-Stage  Air  Compression, i75 

CHAPTER  XIII. 
The  Expansion  of  Compressed  Air  and  the  Work  of  the  Motor,  .  195 

CHAPTER  XIV. 
Transmission  of  Power  by  Compressed  Air, 211 

CHAPTER  XV. 
Compressed  Air  Reheating  and  its  Work 223 

CHAPTER  XVI. 
The  Compressed-Air  Motor 241 


Xll  CONTENTS. 

CHAPTER  XVII.  PAGE 

Efficiency  of  Air  Compressors  at  High  Altitudes 255 

CHAPTER  XVIII. 
AiK  Compressors  (Descriptive) 269 

CHAPTER  XIX. 
Air  Compressors— Continued, 291 

CHAPTER  XX. 
Air  Compressors — Continued 337 

CHAPTER  XXI. 
Air  Compressors — Continued, 367 

CHAPTER  XXII. 
Compressed  Air  in  Mining  and  Quarrying 415 

CHAPTER  XXIII. 
Pneumatic  Tools — The  Pneumatic  Hammer  and  its  Work,        ,         .         .  ^45 

CHAPTER  XXIV. 

Pneumatic  Tools — Continued,   .         .         .         .         .         ...         .         .         .  497 

CHAPTER  XXV. 
Air  as  Applied  to  Pyrometry. 553 

CHAPTER  XXVI. 
Compressed  Air  in  Railway  Service, 571 

CHAPTER  XXVII. 
Pneumatic  Work, 611 

CHAPTER  XXVIII. 
Pneumatic  Work — Continued,  ..........  627 

CHAPTER  XXIX. 
Pneumatic  Work — Continued,  ..........  661 

CHAPTER  XXX. 
The  Pneumatic  System  of  Tube  Transmission 673 

CHAPTER  XXXI. 
Compressed  Air  in  Warfare,    ..........  693 

CHAPTER  XXXII. 
Compressed  Air  Work,       ...........   709 

CHAPTER  XXXIII. 
Refrigeration, 745 

CHAPTER  XXXIV. 
The  Hygiene  of  Compressed  Air 773 

CHAPTER  XXXV. 
Liquid  Air,  its  Properties  and  Uses, 7S5 

CHAPTER  XXXVI. 
List  of  Patents  from  1S75  to  July,    igai, 803 


Chapter  I. 


HISTOR  ICAL 


HISTORICAL. 

The  use  of  air  iii  its  lower  condition  of  compression  for 
power  and  for  mechanical  purposes  has  been  known  from  the 
earliest  ages,  and  antedates  any  knowledge  we  possess  of  the 
use  of  steam  by  many  generations. 

The  reduction  of  metals  from  their  ores  and  the  forging  of 
iron  and  steel  brought  the  forge  and  the  blast  furnace,  with  the 
use  of  air  under  pressure,  into  existence  as  mechanical  appli- 
ances more  than  two  thousand  years  before  the  Christian  Era. 

The  evidences  of  the  use  of  the  air  blast  under  compression 
are  plainly  seen  depicted  on  the  sculptured  walls  of  the 
structures  of  the  oldest  civilization,  and  are  made  still  more 
manifest  in  its  endurated  paintings  and  in  the  legends  of  the 
early  historians. 

The  first  inception  of  air  power,  as  gathered  from  the 
example  of  the  wands,  seems  to  have  been  less  progressive  in 
its  uses  than  other  of  the  mechanical  arts;  for,  while  it  formed 
one  of  the  vital  elements  in  producing  the  metals,  the  inventive 
instinct  in  handicraft  seems  also  to  have  been  instilled  in  the 
early  workers  of  metals  in  creating  the  tools  that  by  the 
ancient  genius  of  art  worked  out  the  models  of  beauty  that  are 
our  examples  of  to-day. 

The  old  methods  of  compressed-air  production  seem  to 
have  taken  on  a  crude  and  nearly  stationary  form  for  at  least 
two  thousand  years  before,  and  for  more  than  a  thousand  years 
after,  the  Christian  Era,  and  in  some  parts  of  the  world  may  be 
seen  in  operation  to  this  day. 

In  China,  India,  Burmah,  Borneo,  Africa,  and  Madagascar 
the  primitive  methods  of  compressing  air  are  still  in  use :  the 


i6  compressp:i)  air  and  its  applications. 

air  treading  bags,  the  wooden  cylinder  and  piston,  and  the 
Chinese  wind-box  are  the  common  devices  for  producing  the 
air  blast. 

The  only  further  progress  that  appears  on  record  in  regard 
to  the  production  of  compressed  air  and  its  uses  for  power 
purposes  has  been  handed  down  in  fragmentary  history,  and 
mostly  contained  in  the  pneumatics  of  Heron  of  xVlexandria. 

From  the  descriptions  extant,  he  seems  to  have  been  the 
first  to  invent  or  to  describe  the  pressure  air  pump  or 
compressor  for  pressures  greater  than  the  forge  blast,  and  to 
have  applied  it  in  the  famous  fountain  attributed  to  him. 
Notwithstanding  the  alleged  ignorance  of  the  ancients  respect- 
ing the  physical  properties  of  the  atmosphere,  there  are 
circumstances  related  in  history  which  seem  to  indicate  the 
reverse ;  for  Diogenes  of  Apollonia  reasoned  on  its  condensa- 
tion and  rarefaction. 

The  description  of  the  fire  engine  of  the  Egyptians,  as 
given  in  Heron's  "  wSpiritalia,"  shows  very  plainly  that  the  use 
of  air  compression  and  its  elasticity  in  the  air  chamber  of  a 
hydraulic  pump  were  well  understood  in  the  second  century  be- 
fore the  Christian  Era. 

The  devices  of  the  Egyptian  priesthood  for  exciting  the 
wonder  and  awe  of  the  people,  possessed  as  they  were  of  the 
superstitions  and  proclivities  of  that  age,  were  no  doubt  derived 
from  a  general  knowledge  of  many  of  the  physical  laws  of  the 
elements  possessed  by  the  ruling  and  priestly  classes. 

They  understood  the  nature  of  the  expansion  and  contrac- 
tion of  air  by  heat  and  cold,  of  which  the  vocal  statue  on  the 
plain  of  Thebes  was  an  example. 

Th?,  movement  of  the  statue  of  Serapis  and  the  altar  tricks 
of  the  Pharaonic  priesthood  are  other  examples  of  the  designed 
antics,  due  to  the  use  of  compressed  air  and  the  vapor  of 
water. 

Had  it  not  been  for  the  written  work  of  Heron,  the  "  vSpir- 
italia,"  we  should  never  have  suspected  that  air  was  made  to 


HISTORICAL.  17 

perform  so  important  a  part  in  ancient  frauds,  nor  that  its 
compression  and  expansion  had  been  employed  to  raise 
liquids. 

Notwithstanding  the  high  opinion  which  history  gives  us  of 
the  historical  and  philosophical  knowledge  of  the  old  Egyptian 
priesthood,  we  should  hardly  have  surmised  that  they  had  the 
art  of  applying  this  subtle  fluid  so  ingeniously.  They  seem, 
however,  to  have  searched  all  nature  for  devices ;  and  to  have 
become  familiar  with  many  of  the  principles  upon  which  the 
most  valuable  of  our  arts  and  mechanics  are  based. 

The  condensing  air  pump  or  compressor  must  have  been 
used  in  charging  the  wind  guns  of  Ctesibius  of  Alexandria, 
about  120  B.C.,  as  described  by  Vitruvius.  The  properties 
exhibited  by  a  partial  vacuum  must  have  been  well  known  from 
five  hundred  to  one  thousand  years  before  the  Christian  Era,  as 
illustrated  in  the  use  of  the  siphon  and  the  atmospheric  water- 
ing-pots of  the  early  Egyptians,  though  the  principle  of  the 
perfect  vacuum  is  undoubtedly  due  to  Torricelli,  by  his  produc- 
tion of  the  mercurial  vacuum,  about  1643  a.d. 

The  air-pressure  bellows,  in  its  many  forms,  seems  to  have 
been  confined  to  a  stated  use,  that  of  forcing  a  fire,  from  the 
earliest  times,  when  a  slight  advance  was  made  in  air  pressure 
to  operate  the  devices  and  toys  used  in  priestly  incantations, 
followed  by  its  application  in  the  propulsion  of  projectiles  by 
Ctesibius. 

Then  its  principles  slumbered  in  its  low-pressure  use  for 
more  than  a  thousand  years,  when  the  arrow  discharged  under 
air  pressure  by  Ctesibius  finally  developed  into  the  pneumatic 
gun  of  Marin  in  France,  which  was  presented  to  Henry  IV.  :n 
1600.  A  more  perfect  compressed-air  gun  was  brought  out  by 
Guter  at  Nuremberg  in  1656,  which  had  attached  to  the  stock, 
in  musket  form,  all  the  appliances  for  charging  and  discharging 
by  air  compression.  But  little  further  progress  was  made  in 
this  line  until  near  the  middle  of  the  nineteenth  century,  when 
compressed-air  guns  took  a  wide  range  of  design;  their  most 


l8  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

useful    and    effective    outcome    being    the   pneumatic   guns  of 
Zalinski  and  others. 

While  the  mechanic  arts  slumbered  through  the  dark  ages 
in  Europe,  the  Chinese  seem  to  have  improved  the  aboriginal 
piston  blower  by  a  more  perfect  action  and  finish,  in  an  instru- 
ment styled  by  them  the  "wind-box." 

The  water  trombe,  or  tromp,  for  compressing  air  by  a  fall 
of  water  in  a  tube,  used  for  blowing  forges  and  other  purposes, 
was  known  to  Heron,  and  was  mentioned  by  Pliny  in  his 
"Natural  History." 

In  improved  form  the  tromp  has  held  its  place  for  two 
thousand  years,  and  is  in  use  at  the  present  day  in  Europe  and 
the  Orient. 

The  principle  of  Heron's  pneumatic  fountain  for  raising 
water  was  carried  out  on  a  large  and  useful  scale  in  the  pneu- 
matic pumping  engine  at  the  mines  of  Chemnitz,  in  Hungary, 
erected  by  M.  Hoell  in  1755;  there  was  probably  first  illus- 
trated the  refrigerating  power  of  air  when  expanded  from  great 
pressure.  In  the  lower  chamber  of  this  apparatus  the  discharge 
of  air  and  its  expansion  with  water  produced  hail  or  pellets 
of  ice.  At  first  this  machine  required  personal  attention  in  its 
manipulation,  but  in  1796  it  was  made  automatic. 

The  use  of  compressed  air  for  submarine  work  was  no  doubt 
well  known  in  the  earliest  ages,  being  almost  coeval  with  the 
dawn  of  commerce. 

Aristotle  (350  B.C.)  describes  a  kettle  in  which  divers  sup- 
plied themselves  with  fresh  air  under  water.  The  legend  of 
the  descension  of  Alexander  the  Great  to  the  bottom  of  the  sea 
in  a  vessel  called  a  colyvtpia,  with  a  glass  window  in  it,  is  no 
doubt  an  allusion  to  the  use  of  the  diving-bell.  It  was  em- 
ployed in  Phoenicia  in  the  year  320  B.C.,  and  the  use  of  glass 
was  well  known  then. 

Nothing  further  appears  on  record  in  regard  to  submarine 
work  with  a  bell  for  more  than  fifteen  hundred  years,  when 
mention  of  its  use  in  vSpain  in   1538  is  met  with.     Bacon  de- 


HISTORICAL,  19 

scribes  it  (1620)  as  a  machine  used  to  assist  persons  laboring 
under  water  upon  wrecks,  affording  a  reservoir  of  air  into  which 
they  could  enter  to  take  breath. 

From  this  time  on  for  a  hundred  years  the  diving-bell  was 
largely  used  in  Europe  in  recovering  wreckage  and  treasure; 
in  17 1 5  Dr.  Halley  made  the  first  contrivance  for  supplying 
the  diving-bell  with  fresh  air  by  lowering  air-filled  barrels  and 
discharging  the  air  under  the  bell,  letting  out  the  foul  air  at 
the  top  through  a  cock;  or  of  allowing  of  completely  filling 
the  space  with  air  that  was  made  unavailable  heretofore  by  the 
compression  of  the  air  in  the  bell. 

Dr.  Halley  suggested  the  present  system  of  submarine 
armor  by  using  a  cap  or  portable  helmet  connected  with  a 
tube  leading  to  the  surface,  through  which  fresh  air  was  forced 
to  the  helmet  for  the  needs  of  the  diver.  Smeaton  and  Brunei, 
from  1779  on,  improved  on  the  use  of  the  diving-bell,  making 
its  operation  continuous  by  a  fresh  supply  of  compressed  air 
through  tubes  from  pumps. 

The  submarine  armor  continued  to  be  improved  along  the 
lines  of  its  present  form  for  deep-sea  work,  in  which  depths  of 
148  feet  have  been  attained,  involving  work  under  an  air 
pressure  of  65  pounds  per  square  inch  for  several  hours.  It 
has  been  claimed  that  a  depth  of  200  feet  has  been  reached 
without  serious  results  from  the  great  pressure  due  to  that 
depth. 

The  compressed-air  and  vacuum  pump  was  greatly  im- 
proved by  Otto  Van  Guericke  about  1650,  and  it  has  been 
claimed  as  his  invention. 

Savary  increased  the  pressure  of  air  for  blast  furnaces  by 
the  use  of  more  substantial  blowers,  in  the  latter  part  of  the 
seventeenth  century. 

Denys  Papin  was  the  first  to  propose  and  make,  in  1653, 
an  actual  trial  of  the  transmission  of  power  to  a  distance  by 
compressed  air.  His  early  ideas  being  finally  developed  into 
more  practicable  shape,  they  resulted  in  his  recommending  the 


20  COiMPRESSED    AIR    AND    ITS    APPLICATIONS. 

use  of  water  j^o^ver  for  compressing  air  and  forcing  it  to  a 
distance  for  useful  work,  tlius  foreshadowing  the  now  common 
practice  of  the  long  transmission  and  distribution  of  air  through 
mines  for  the  operation  of  machinery. 

His  system  of  an  air  pump  driven  by  a  water  wheel,  oper- 
ating on  air  and  water  chambers  at  a  distance,  was  in  the  right 
direction,  but  failed  in  its  practical  operation  by  the  elasticity 
of  the  air,  which  he  had  intended  to  use  as  a  long  piston  in 
transmitting  power  from  an  air-working  piston  to  a  distant 
water  piston. 

It  was  the  fertile  and  mechanical  brain  of  Papin  that  jfirst  con- 
ceived the  idea  of  the  pneumatic  tube  for  transmitting  parcels  by 
air  pressure,  thus  antedating  by  more  than  two  hundred  years 
our  pneumatic-tube  postal  and  package  service,  and  thus  early 
opening  the  way  for  future  advancement  in  the  use  of  com- 
pressed air. 

Experiments  were  made  in  Wales  in  these  early  years  to 
utilize  water  power  for  compressing  air  and  transmitting  it 
long  distances  for  operating  blast  furnaces. 

In  1757,  Wilkinson,  in  England,  patented  a  method  of  com- 
pressing air  by  the  use  of  a  column  of  water,  effecting  his 
object  by  means  of  a  series  of  chambers  or  water  compressors, 
used  one  after  another,  so  as  to  keep  up  a  regular  pressure ; 
thus,  in  a  crude  way,  preceding  by  a  hundred  years  the  water 
compressor  of  Sommeiller  at  the  Mont  Cenis  tunnel. 

Many  vague  descriptions  of  apparatus  for  the  use  of  com- 
pressed air  in  the  mechanic  arts  and  for  its  compression  are 
found  in  the  English  patents  during  the  eighteenth  century; 
but  either  their  practical  applications  were  never  realized  or 
else  no  record  was  made  of  their  operation. 

The  application  of  compressed  air  to  practical  uses  and  its 
transmission  for  power  purposes  seem  to  have  commenced  an 
era  of  advancement  in  the  last  years  of  the  eighteenth  century. 

Professor  St.  Clair,  of  the  Edinburgh  University,  in  1785, 
proposed    attaching    air  bags    to    sunken    vessels    beneath   the 


HISTORICAL.  2  1 

surface  of  the  water  and  inflating  them  by  air  pumps;  fol- 
lowed by  its  practical  use  for  raising  vessels,  for  which  many 
patents  have  been  issued  in  Europe  and  the  United  States  for 
various  modifications  of  this  device.  Its  most  successful  trials 
were  made  in  1864  in  raising  a  steamer  sunk  in  Lake  Boden, 
and  in  raising  the  vessels  sunk  at  Sebastopol  during  the 
Crimean  War. 

From  that  time  on  many  patents  have  been  issued  for  vari- 
ous devices  for  raising  vessels  by  inflating  floats  by  air  pressure, 
and  for  compressing  air  and  its  use  in  diving-bells  and  sub- 
marine armor. 

Medhurst,  a  Danish  engineer  in  England,  in  1799  com- 
pressed air  to  15  atmospheres  (210  pounds),  stored  and  trans- 
mitted it  to  a  motor  in  a  mine ;  he  patented  a  pneumatic  system 
for  conveying  persons  and  parcels  in  tubes  in  18 10,  followed  by 
publications  during  a  period  of  several  years  on  tubular  trans- 
mission by  compressed  air.  There  is  no  record  of  the  practical 
working  of  the  many  schemes  of  this  fertile  genius. 

Compressed  air  for  driving  vehicles  seems  to  have  had  its 
birth  with  the  beginning  of  the  nineteenth  century  in  a  patent 
to  Medhurst,  in  England,  August  2,  1800,  for  means  for  propel- 
ling carriages  by  compressed  air  from  a  reservoir. 

Compressed  air  for  tramway  cars  appears  to  have  received 
an  impulse  in  Wright's  English  patent,  April,  1828;  he  also 
proposed  the  use  of  iron  cylinders  beneath  the  cars,  with  an 
additional  cylinder  for  heating  the  air  by  a  small  furnace,  to 
increase  its  expansive  force  before  entering  the  working  cylin- 
der and  to  mingle  steam  generated  by  the  same  furnace  with 
the  hot  air. 

The  air  brake  seems  to  have  first  taken  shape  at  this  time  in 
Wright's  patent  with  an  eccentric  on  a  wheel  shaft,  connected 
with  a  piston,  which  was.  to  be  operated  as  a  brake  on  down- 
grades by  pumping  air  into  the  air  chambers ;  but  it  was  not 
until  1 869  that  air  brakes  began  to  take  a  practical  form  under 
the  patents  of  Westinghouse. 


22  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

In  1828,  Bompass,  in  England,  patented  and  built  a  com- 
pressed-air locomotive. 

Parsey,  in  1847,  built  and  ran  a  vehicle  in  which  an  inter- 
mediate reservoir  was  provided  for  reducing  and  equalizing  the 
air  pressure  to  the  cylinders.  Baron  von  Rathlen  built  and 
ran  a  vehicle  with  compressed  air  in  England  in  1848,  attaining 
a  speed  of  12  miles  per  hour  on  the  best  roads  of  that  day;  he 
also  suggested  an  increased  pressure  to  750  pounds  per  square 
inch  as  desirable  for  road  and  locomotive  power,  and  advised 
compound  compression  and  intercooling. 

The  earliest  known  appliance  for  making  ice  by  the  expan- 
sion of  compressed  air  was  invented  and  put  inio  actual  practice 
by  Dr.  John  Gorrie,  of  New  Orleans,  La.,  in  1850,  to  whom  a 
patent  was  issued  in  185  i.  The  system  of  cold-room  storage 
by  the  expansion  of  compressed  air  has  since  been  greatly 
enlarged  on  the  lines  originated  by  Dr.  Gorrie,  and  is  in  use 
in  the  meat  and  fruit  transport  service. 

Vallance  again  agitated  the  subject  of  tube  transmission  in 
England,  in  18 18  and  on,  and  proposed  a  cast-iron  tube  system 
for  passengers  and  parcels ;  followed  by  others  with  feeble  ef- 
forts to  establish  the  pneumatic  tube  system  from  about  1824; 
and  again  by  William  ]\Iann  with  English  patents  in  1824. 

It  was  not  until  about  1865  that  practical  success  was  achieved 
by  the  Parcel  Dispatch  Compan}^  of  London ;  since  then  the 
use  of  this  system  for  parcel  and  postal  transmission  has  been 
greatly  developed  in  Europe  and  in  the  L^nited  States. 

The  first  compound  compression  of  air  was  probably  sug- 
gested in  the  patent  to  William  ]\Iann  in  1829,  for  what  was 
then  called  stage  pumping,- — /.r.,  the  use  of  two  or  more  cylin- 
ders with  intercooling ;  which  was  then  properly  claimed  not 
only  to  effect  great  economy  in  compressing  air,  but  also  to  de- 
crease the  machinery  strain  and  to  admit  of  lighter  construc- 
tion of  the  compressor. 

In  1830  and  on,  Clegg  and  Pinkus,  in  England,  agitated  the 
system  of  a  slotted  tube  and  travelling  piston  with  a  vacuum  or 


HISTORICAL.  23 

air  pressure,  with  connections  to  an  outside  carriage.  Experi- 
ments were  carried  on  through  several  years  without  success, 
although  trials  were  made  with  short  lines  of  slotted  air  tubes 
in  England  and  Ireland. 

In  1830,  Thilorier  compressed  gases  to  high  pressures  in 
stages,  for  which  he  received  a  medal  from  the  French 
Academy. 

The  air-plunger  pump  for  producing  fire  by  compressed 
air  was  a  family  adjunct  before  friction  matches  came  into  use, 
in  the  home  of  the  writer's  father,  who,  in  1833,  employed  an 
apparatus  made  by  himself,  consisting  of  a  cast-iron  barrel 
weighing  several  pounds,  wdth  a  bore  three-eighths  of  an  inch 
in  diameter,  like  a  cannon  without  the  vent.  A  steel  piston, 
about  eight  inches  long,  was  accurately  and  tightly  fitted,  but 
moved  rather  easily  when  lubricated.  The  end  of  the  piston 
had  a  small  cavity  for  receiving  a  piece  of  punk  ;  the  handle  was 
provided  with  a  stop  or  shoulder  to  prevent  the  plunger  from 
striking  the  bottom  in  its  sudden  movement.  The  weight  of 
the  barrel,  pushed  by  hand,  acted  by  its  momentum  to  complete 
the  final  pressure  of,  probably,  eight  hundred  or  more  pounds 
per  square  inch,  with  an  instantaneous  evolution  of  temperature 
to  a  red  heat,  which  fired  the  punk.  A  quick  withdrawal  of 
the  plunger  and  the  touch  of  a  sulphur  match  completed  the 
operation  of  generating  a  fire. 

Following  the  agitation  of  the  slotted-tube  system  of  Clegg 
and  Pinkus,  in  1830,  the  subject  was  revived  by  Count  Fon- 
tainemoreau,  in  1844,  and  trials  were  made  with  unsatisfactory 
results. 

The  parcel-tube  transmission  system  was  again  brought  to 
the  surface  in  England  about  i860.  A  thirty-inch  tube,  a 
quarter  of  a  mile  in  length,  was  constructed  at  Battersea,  and 
afterward  removed  to  London  and  used  for  conveying  the  mail 
between  district  offices. 

This  was  followed  in  1864  by  a  larger  and  longer  line  in 
London. 


24  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

The  trials  of  ^Ir.  A.  E.  Beach  in  New  York,  in  1867,  with 
an  eight-foot  subway  under  Broadway  for  the  propulsion  of 
passenger  cars  by  air  pressure,  seemed  a  step  in  the  right  di- 
rection, and  failed  only  from  apathy  in  financial  circles. 

The  pneumatic-tube  system  simply  slumbered  for  a  time, 
and  was  then  developed  into  its  most  useful  work;  at  the  pres- 
ent time  it  is  largely  in  use  for  interpostal  and  telegraphic-office 
connections  throughout  Europe  and  the  United  States.  The 
store  cash  system,  in  its  intricate  detail,  promptness,  and  ac- 
curacy, is  a  modern  wonder. 

Compressed  air  for  machine-driving,  crane-hoisting,  and 
other  mechanical  purposes  was  agitated  in  England  in  1840  and 
on,  with  patents  on  detail  plants  for  the  transmission  of  com- 
pressed air  from  a  central  station  to  distant  hoisting  engines  in 
warehouses  and  on  docks.  Ericsson,  in  1858,  compressed  air 
by  the  power  of  caloric  engines,  for  operating  hoisting-engines 
in  warehouses  in  New  York,  followed  by  a  practical  system  for 
running  sewing-machines  in  large  numbers  from  a  central 
station  by  the  transmission  of  compressed  air  to  small  motors 
on  the  machines. 

Compressed  air  for  high  working  pressures,  generated  by 
hydraulic  pressure  and  the  use  of  waterfalls,  was  an  improve- 
ment on  the  antiquated  methods  by  the  use  of  the  trompe. 

The  direct  pressure  system  was  brought  into  use  by  Som- 
meiller  at  the  Mont  Cenis  tunnel  in  1872,  and  did  good  work  at 
that  time;  but  as  it  required  as  much  water  to  compress  the  air 
as  was  equal  to  the  amount  of  free  air  compressed,  the  system 
was  applicable  only  in  favorable  localities,  and  has  now 
dropped  out  of  use.  Many  patents  have  since  been  issued  on 
direct-acting  hydraulic  air  compressors,  but  the  principle  is  not 
economical  in  practice,  and  we  know  of  no  compressors  of  this 
class  in  use  at  the  present  time. 

The  trompe  system  has  been  greatly  improved  and  extended 
for  high  pressure,  with  a  large  flow  of  water  with  moderate 
head,  by  making  a  deep  pit  with  an  air  chamber  at  the  bottom 


HISTORICAL.  25 

and  returning  the  water  to  the  foot-fall  as  in  an  inverted 
siphon.  This  was  first  demonstrated  in  experiments  by  Mr.  J. 
P.  Fizell,  of  Boston,  in  1877.  and  patented  in  1878.  It  has  been 
finally  put  in  practical  operation  by  Mr.  C.  H.  Taylor  in  large 
instalments  of  hydraulic  plants  at  Magog,  near  Montreal,  and 
at  Ainsworth,  British  Columbia. 

Both  plants  have  proved  a  success,  and  the  utilization  of 
water  pow-er  for  compression  of  air  and  its  transmission  for  all 
power  purposes  is  thereby  assured. 

The  vertical  excavated  shafts  may  not  be  needed  where 
steep  slopes,  or  chasms,  or  mountain  sides  are  available.  The 
moving  water  will  carry  air  down  a  slope  as  well  as  by  vertical 
shaft,  and  the  return  pipe  only  follows  the  same  line  back,  so 
that  the  friction  due  to  the  additional  length  of  flow  line  is  the 
cnly  loss  in  efliicency. 

Compressed  air  for  street  railways  was  continually  agitated 
by  newspapers  and  promoters  during  the  middle  of  the  nine- 
teenth century.  But  little  practical  progress  was  made,  much 
of  the  difficulties  and  obstructions  being  due  probably  to  the 
distrust  of  the  moneyed  interest  of  schemes  that  had  no  practical 
and  reliable  tests  and  trials. 

In  1862  the  writer  made  plans  for  a  light  car  street-railway 
system  with  compressed-air  storage  under  the  seats  and  on  top 
of  the  car,  with  the  engine  under  the  platform,  so  that  the 
passenger  accommodation  was  not  interfered  with.  The  air 
pressure  of  two  hundred  and  fifty  pounds  was  to  be  supplied 
from  station  storage  tanks  and  a  compressor  on  the  line.  The 
plans  did  not  meet  with  financial  encouragement,  and  proved 
to  be  premature.  The  horse  was  not  yet  ready  to  go.  Another 
generation  was  needed  to  bring  compressed-air  power  for  rail- 
ways to  a  financial  acceptance. 

Further  progress  was  made  about  1873  in  the  intercooling 
of  the  compressing  air  in  the  cylinders  by  water  jets  or  sprays, 
in  the  compressors  at  the  vSt.  Gothard  tunnel.  This  led  to  still 
further  improvements  and  economics  in  the  construction  of  air- 


26  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

compressing  machines;  until  at  the  present  day  there  seems  to 
be  nothing  but  change  of  detail  in  construction — that  may  not 
always  result  in  improvement. 

The  introduction  of  compressed-air-hauling  locomotives  in 
the  St.  Gothard  tunnel  was  a  successful  turn  in  favor  of  com- 
pressed air  for  railway  work,  and  seemed  to  stimulate  efforts 
in  that  direction ;  it  was  soon  followed  by  the  Mekarski  and 
Beaumont  compressed-air  railway  systems  in  Europe,  with 
increased  air  pressure  and  better  appliances  for  economical 
compression  and  motor  use.  Compressed-air  locomotives  for 
mine  haulage  continued  to  improve  in  constructive  details,  and 
are  now  largely  in  use  in  the  United  States.  For  mining  pur- 
poses compressed-air  appliances  have  been  steadily  perfected, 
until  at  the  present  day  there  seems  to  be  little  room  left  for 
greater  improvement  except  changes  in  detail,  if  such  can  be 
really  called  improvement. 

The  use  of  compressed-air  machinery  for  quarrying,  min- 
ing, and  tunnelling,  and  the  means  of  compressing  air  along 
economical  lines,  have  been  greatly  extended  by  the  inventive 
genius  of  Burleigh,  Ingersoll,  Sergeant,  Rand,  Clayton,  and 
others,  who  have  contributed  to  and  promoted  the  economy  of 
practical  operation  in  rock-boring  machinery  that  has  so  greatly 
aided  in  excavating  the  vast  system  of  railway  tunnels  of  the 
United  States,  and  in  sinking  and  drifting  in  the  mines  of  all 
countries  during  the  past  quarter  of  a  century. 

Every  implement  required  in  the  generation  of  compressed- 
air  power  and  its  uses  has  overflowed  its  earlier  and  narrow 
field  of  work,  and  is  now  encompassing  a  wide  area  of  useful- 
ness in  our  workshops,  factories,  and  in  hundreds  of  industrial 
operations:  transportation,  railway  appliances,  refrigeration — 
even  unto  the  painting  of  buildings  and  structural  work,  and 
the  dusting  of  furniture,  carpets,  and  clothing. 

The  later  development  and  actual  application  of  compressed 
air  at  extremely  high  pressures,  and  its  economical  use  by 
reheating,    derived    from    the    persistent    efforts  of    ^lekarski, 


HISTORICAL.  27 

Beaumont,  and  others  in  Europe,  and  of  Judson,  Hoadley, 
Knight,  and  Hardie  in  the  United  States,  have  brought  the  use 
of  compressed  air  to  a  new  condition  of  application,  and  a  high- 
pressure  storage  of  2,500  or  more  pounds  per  square  inch  in  a 
condensed  space  of  from  170  to  180  volumes  in  one  volume. 
This  allows  for  sufficient  storage  volume  within  the  limit  of 
passenger-car  and  vehicle  capacity  for  runs  of  reasonable 
distances. 

The  precise  limit  of  the  compressibility  of  air  at  ordinary 
temperatures  is  as  yet  an  unknown  quantity.  It  has  been  com- 
pressed to  14,000  pounds  per  square  inch  in  experiments  for 
blasting  rock;  and  it  has  been  asserted,  and  there  seems  to 
be  no  reason  to  doubt,  that  any  pressure  may  be  obtained 
within  the  limit  of  safety  in  the  strength  of  metals  to  hold  the 
pressure. 

'The  assertion  has  been  made  by  experimenters  with  high 
air  pressures  that  20,000  or  more  pounds  per  square  inch  may 
be  made  available  for  special  purposes ;  this  is  far  below  the 
explosive  power  of  gunpowder. 

The  blasting  effect  of  air  at  high  pressure  in  coal  mines 
was  noted  in  a  series  of  trials  at  Denton  and  Wigan,  England, 
in  1877-79. 

During  these  trials  a  pressure  of  14,200  pounds  per  square 
inch  was  attained  by  the  comparatively  crude  methods  of  those 
days.  As  compared  with  powder,  the  trials  were  successful  in 
the  saving  of  time  and  in  the  health  and  safety  of  the  men ; 
but  the  cost  of  production  exceeded  that  of  explosives,  and  the 
scheme  was  abandoned. 

The  experiments  in  high  air  pressures  conducted  by  Mr. 
Perkins,  a  noted  engineer,  in  England,  and  detailed  in  a  paper 
read  to  the  Royal  Society,  June  15,  1826,  are  most  interesting, 
as  demonstrating  the  liquefaction  of  air  at  ordinary  temperature. 

Mr.  Perkins  used  a  cast-steel  pump,  tested  to  2,000  atmos- 
pheres, nearly  30,000  pounds  per  square  inch,  with  water. 
Using  the  same  pump  for  air,    he  observed  the  then  curious 


28  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

phenomena  that  induced  him  to  carry  the  compression  of  air  to 
the  highest  limit  possible. 

At  500  atmospheres,  nearly  7,500  pounds,  the  air  began  to 
disappear,  apparently  by  partial  liquefaction ;  at  800  atmos- 
pheres, still  further  liquefaction  was  observed;  at  1,000  atmos- 
pheres, 14,700  pounds,  small  globules  of  liquid  air  formed  in 
the  tube;  and  at  1,200  atmospheres,  17,640  pounds  per  square 
inch,  a  beautiful  transparent  liquid  was  seen  in  the  glass 
compression  tube. 

Few  attempts  were  made  to  liquefy  air  for  many  years  suc- 
ceeding Perkins'  experiments,  until  about  1877,  when  Raoul 
Pictet,  Cailletet,  Dewar,  Olzewski,  and  others  followed  in  the 
line  of  producing  liquid  air  by  the  cold  or  low-temperature 
process  and  moderate-compression  system. 

Michael  Faraday  had  been  experimenting  on  the  liquefac- 
tion of  air  and  other  gases  since  1823  with  indifferent  results. 
More  recently  Professor  Linde,  in  Germany,  has  by  improved 
and  larger  appliances  liquefied  air  in  large  quantities. 

Tripler  and  others  in  the  United  States  have  made  liquid 
air  a  commercial  commodity. 

Its  practicability  as  a  motive  power  has  been  doubtingly 
questioned,  and  even  ridiculed;  but  the  fact  is  in  evidence  that 
it  has  the  qualifications  of  a  power  mover,  and  can  be  controlled 
for  any  required  pressure.  Its  practicability  and  economy  are 
now  being  tested ;  as  a  refrigerant,  its  power  is  amazing. 

The  number  of  United  States  patents  for  compressed-air 
devices  and  appliances  has  gradually  increased  during  the  past 
century,  and  is  now  upward  of  four  thousand. 


Chapter  II. 


THE 

PHYSICAL    PROPERTIES 

OF  AIR 


THE     PHYSICAL    PROPERTIES   OF    AIR. 

Air  as  it  exists  at  and  near  the  surface  of  the  earth  is  a 
mechanical  compound  or  mixture  of  several  gases,  principally 
nitrogen,  filling  79  parts  by  volume,  or  'j'j  parts  by  Aveight, 
and  oxygen,  approximately  21  parts  by  volume,  or  23  parts  by 
weight.  The  relative  volumes  of  nitrogen  vary  to  an  amount 
of  about  five  per  cent  in  different  localities. 

In  air  expelled  from  water  by  heating,  Bunsen  found  34.9 
parts  by  volume  of  oxygen  and  65.  i  parts  by  volume  of  nitrogen. 
This  change,  made  by  contact  with  water,  in  the  constituent 
volumes  of  air  may  be  partly  accounted  for  by  the  absorption 
of  the  carbonic  acid  gas  and  the  formation  of  ammonia  from  the 
nitrogen  of  the  air  and  hydrogen  from  the  water,  which  would 
liberate  oxygen. 

This  singular  change  in  the  constituents  of  air,  when 
absorbed  b\^  water,  may  have  an  important  bearing  upon  the 
existence  of  marine  life  that  we  have  not  yet  seen  discussed. 

A  minute  percentage  of  from  .002  to  .005  of  carbonic  acid 
gas,  a  lesser  amount  of  ammonia,  and  the  newly  discovered 
argon,  amounting  to  about  one  per  cent,  in  volume,  are  always 
present  in  air.  The  vapor  of  water  is  ever  present  in  the 
atmosphere  at  seldom  less  than  50  per  cent  of  saturation,  at 
which  point  it  holds  .00044  of  a  pound  of  water  per  cubic  foot 
of  air  at  62°  F. ;  and  at  the  point  of  saturation  and  temperature 
of  62°  F.  it  holds  .00088  of  a  pound  per  cubic  foot  of  air. 

The  expression  of  "dry  air,"  used  by  our  air-compressor 
friends,  is  only  relative,  and  air  can  only  be  considered  dry  when 
the  amount  of  moisture  is  at  less  than  50  per  cent  of  saturation 
for  any  given  temperature;  the  amount  of  moisture  actually 
varies  with  the  temperature  to  three  times  less  at  32°  F.  to 
three  times  more  than  the  above  figures  at  92°  F. 


32  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

Air  is  absorbed  by  water  in  a  decreasing  ratio  from  32°  F. 
upward  to  a  temperature  at  which  vapor  becomes  visible  and  at 
atmospheric  temperature.  Increased  absorption  of  air  by  water 
takes  place  under  increasing  pressure;  hence,  the  frequent  loss 
of  air  in  the  air  chambers  of  pumping-machines  and  water  rams. 

TABLE    I. — Comparative   Volume  of   Air   Absorbed    i;v  Water  at  Various 
Temperatures,  in  Volumes. 


32    F 0.02471 

41       02179 

50      01953 

59       o'795 


68    F  0.01704 

77       01632 

86       01556 


To  the  loss  of  air  in  free  running  water  at  the  higher  tem- 
peratures in  the  table  is  probably  due  the  insipidity  of  such 
water  as  compared  with  its  taste  between  the  temperatures  of 
32°  and  41°  F. 

The  weight  of  absolutely  dry  air  at  the  sea  level  in  middle 
latitudes  and  mean  barometric  pressure  of  29.92  inches  and  at 
32°  F.,  is  .080728  pounds  per  cubic  foot;  at  62°  F.  it  weighs 
.0761  pounds  per  cubic  foot,  and  is  819.5  times  lighter  than 
water,  which  weighs  62.355  pounds  per  cubic  foot  at  the  same 
temperature,  viz.,  62°  F. 

Air  at  the  barometric  pressure  of  29.92  inches,  14.7  pounds 
per  square  inch,  or  2166.8  pounds  per  square  foot,  and  at  the 
temperature  of  62°  F.,  requires  13.141  cubic  feet  to  equal  i 
pound  avoirdupois ;  and  in  ordinary  computation  these  figures 
are  used  for  the  normal  conditions  of  the  atmosphere  at  sea 
level  in  mid-latitudes. 

If  its  whole  volume  were  of  equal  density  with  the  above 
pressure  (14.7)  at  sea  level,  its  limit  of  height  would  be  -Wlrf' 
equal  to  27,816  feet,  a  quantity  used  in  computing  for  atmos- 
pheric head  (h)  in  the  formulas  for  the  flow  of  air  through 
orifices  at  a  mean  temperature  of  62°  F. 

The  height  of  the  atmosphere  appears  to  have  no  determinate 
limit,  but  it  gradually  fades  away  in  density  and  pressure  to  its 
confines  with  interplanetary  space.     At  about  forty  miles  the 


THE    PHYSICAL    PROPERTIES    OF   AIR.  33 

refractive  effect  of  twilight  ceases;  above  that  elevation  the  air 
is  either  too  rare  or  too  pure  from  foreign  particles  to  send  us 
any  perceptible  reflection  or  illumination. 

There  is  abundant  evidence,  however,  from  the  phenomena 
of  meteors  that  the  atmosphere  extends  to  a  height  of  one 
hundred  miles  at  least,  and  it  cannot  be  asserted  positively  that 
it  has  any  well-defined  upper  limit. 

By  virtue  of  the  expansive  force  of  the  air,  it  might  be 
supposed  that  the  air  in  the  upper  atmosphere  would  expand 
indefinitely  into  the  planetary  space.  But  there  are  opposing 
forces  that  seem  to  limit  its  expansion.  In  proportion  as  the 
air  expands  in  the  upper  regions  of  the  atmosphere  its  expan- 
sive force  is  weakened  and  decreased  by  loss  of  heat,  which 
partially  counteracts  its  expansion,  and  with  gravity  probably 
holds  its  limit  near  the  zone  of  absolute  zero  of  temperature. 

Below  the  level  of  the  sea,  as  in  the  valley  of  the  Dead  Sea 
and  in  the  shafts  and  adits  of  deep  mines,  the  density  of  the 
atmosphere  increases  in  the  same  ratio  as  above  the  sea  level 
for  equal  temperatures  and  humidity.  Such  depths  are  indi- 
cated by  the  barometer  under  the  same  conditions  as  for  the 
upper  atmosphere. 

The  atmosphere  obeys  the  law  of  compression  and  expansion 
when  kept  at  a  constant  temperature,  as  found  by  Boyle  and 
Mariotte,  called  Boyle's  law,  or  the  first  law  of  dynamics.  By 
this  law  the  density  of  air  and  the  atmosphere  under  compres- 
sion, whether  from  the  gravity  of  its  own  weight  or  b}-  arti- 
ficial compression,  is  directly  proportional  to  the  pressure  to 
which  it  is  subjected,  when  its  temperature  is  constant  or  at  the 
same  temperature  throughout  the  change  of  volume.  It  follows 
that  when  the  height  above  the  sea  level  increases  by  equal 
intervals  and  for  equal  temperatures  the  density  of  the  air 
decreases  in  a  geometrical  ratio:  thus,  a  cubic  foot  of  air  at  sea 
level  will  become  two  cubic  feet  at  about  18,000  feet  above  the 
sea,  and  four  cubic  feet  at  about  36,000  feet.     This  condition 

of  tenuity   of    the   atmosphere    at    great  heights    is  shown    in 
3 


34  COMPRESSEn    AIR   AND    ITS    APPLICATIONS. 

the  scanty  vegetation,  and  the  difficulty  of  sustaining  life  in 
the  attempts  to  climb  to  the  dizzy  altitudes  of  our  highest 
mountains. 

In  the  process  of  compressing  air  under  the  ordinary  con- 
ditions of  the  atmosphere,  it  becomes  heated  by  compression ; 
and  on  cooling  in  the  compressed  state  becomes  saturated  by 
the  narrowing  limits  of  the  moisture  or  water  vapor  held  in  the 
free  air;  and  on  further  cooling  the  excess  of  moisture  is  set  free 
as  water  in  the  reservoirs  or  pipes  containing  the  compressed  air. 

For  convenience  of  reference  in  regard  to  the  relations  of 
air  and  its  contained  moisture,  the  following  table  shows  these 
conditions  for  differences  of  io°  F.  from  zero  to  the  boiling- 
point  of  water : 

Table  11.  Column  2  gives  the  comparative  volume  of  free  air 
at  different  temperatures  from  its  volume  of  i.  at  32°  F. 

Column  3. — The  weight  of  one  cubic  foot  of  absolutely  dry 
air  at  the  temperatures  in  the  first  colum.n. 

Column  4. — The  elastic  force  of  the  vapor  of  water  alone  in 
inches  of  mercury  at  the  temperatures  in  the  first  column. 

Column  5. — The  elastic  force  of  the  air  alone  in  a  saturated 
mixture  of  air  and  vapor  in  inches  of  mercury.  Its  values  are 
obtained  by  subtracting  the  elastic  force  in  column  4  from  the 
standard  barometric  pressure  at  sea  level;  viz.,  29.92  —  column 
4  =  column  5. 

Column  6. — Represents  the  weight  of  the  air  alone  in  a 
saturated  mixture  of  air  and  vapor ;  it  is  obtained  by  the 
product  of  the  weight  of  a  cube  foot  of  dry  air  in  column  3  and 
the  elastic  force  of  air  alone  in  column  5,  divided  by  the  stand- 
ard barometric  pressure  of  29.921  :   — — —  =  col.  6. 

29.921 

Column  7. — Is  the  weight  in  decimals  of  a  pound  of  vapor 
contained  in  one  cubic  foot  of  saturated  air  at  temperatures  from 
0°  F.  to  212^  F.,  and  is  obtained  by  dividing  the  product  of 
column  3  and  column  4  b}''  the  standard  barometric  pressure  at 
sea  level  (29.921),  and  multiplying  the  quotient  by  the  relative 


THE    PHYSICAL    PROPERTIES    OF   AIR. 


35 


(0   to 

M      C 

to  to 

i-i 

Temperature,  Fah 

heit. 

ren- 

to 

to  to  to 

to 

4-  UJ    to    -■    0  0    00^1    3^(^  4-  <-0    to    M 
to  to  to  to  to  to   to  to  to  to  to  to  to  to  C 

„„««WM««-,-.««                          C 

M 

Volume  of  dry 

air  at  temperatures  m 

first  column. 

to 

LJ    to    to 

C  c«  cr^ 

to 

4- 

totJMwwh-it-iCOOCCOOO 
to   0   CO  04-   to   0   CO  o^4-   to   0   CO  OUJ 
4-4-4-<->iWtOlOlOi-itOOOCCui 

c 

00 

Weight  of 

one  cubic  foot  drv  air 

at  temperature 

in  first  column. 

Hounds. 

o  5 

&- 

o  c  c  c 
M  to  Co  -u 

co  c»  coo 

C'CCCCCCCOCCCCCC 

0^   0  0   C^'^4  ^1^4^-J^J^J^J    COC/iCOCO 
0^    030    C    to  Lki  4-    O^t  0    C    to  4-    0 
C    i-i    t0  4-^J    CW^J    ►-<    C^M^J4-    t0  4- 

to  to 

O  -1- 

« 

^      M      M 

ui   tJ    O 

^J 

04-  U)    to    to    «H    M                                                   C 

Elastic  force 

of  vapor  alone 

Inches  of  mercu 

ry. 

vC    -1- 
tO   'J\ 

to 

CO 

5  c»o 

0 

c 

M^l    o^-^O'-nC^Ji-nWtOtHi-.    C    C 
CM-n    toUiUi    CO    com   cX)a^COi-H^j4_ 
i-n    to    MM    c>i-(    tOLn    OCO^l    i-i    C04-4- 

C  ^n 

- 

<-o  -^  O 

to 

lotototototoiototototototototo 

UJCn    C^^^J    COCOOOOOOOOO 

Ux 

Elastic  force 

of  the  air  alone  in 

the  mixture. 

Inches 
of  mercury. 

> 

> 

C 

> 

PI 

a 

> 
•a 

0 

O  -1- 
O  ^J 

O 
O 

O   "  coo 
c^  r^  to  o 
«  i>j  to  M 

~J     M   W     M     OD4-     CO   1-1   W   <J1     0~J     CO   CO   CO 
en    000    OOtO    tOOO    CM>i  UT  4-    0  4-  ^ 
00    C    0  en   0  0    Oen  UJ  4-   O  w  O  ^ 

0^ 

\\  eight 

of  the  air  in 

pounds. 

a> 

W 

0 

n 

o- 
r.' 

0 
0 

0 

I 

n 
a 

11 

c 

to 

c 

tjx 

ceo 

to  u>  4- 

CO  CN  to 

CO  C  (-►i 

0 
4- 

OOOCCCOOCCCOOOO 
en  en  en    O^  0  C-^J  ^I^J^J^J   cococoO) 

to    C^'-O  '^  f-n    CoO    t04-    OOiO    t04-    O^ 
4_4_0    m04-    O^^-J    04-    to    «    CUl 

b  b 

to  4- 
O  UX 

b 
to 

to 

b  b  b 

to     "     " 

ux    C^4- 
OJ     CO  •-< 
C^  to  1-n 

b  b  b  b  b  b  c  b  c  c  c  b  c  b  b  b 

"OCOOOOOOCCCCOCO 
OcoOM_nU>totO""COOCCCO 
^j4_   O'-'OO    to   oto   coc^4-'-^   to   —   C 
i-H^joo4-4-OtJ'    C>to    CO  to  4-    C    CUJ^J 
OLJO    to    O^J    C~J    M    M-J    04-    to    00 

-»J 

Weight 
of  the  vapor 
in  pounds. 

00 

Total 
weight. 
Pounds. 

0  o 

C«4- 
to  4- 

0 
4- 

-t 

to 

o  o  o 

4-  i-n  ui 
O    to  Ui 

OO     CO   M 

C^  to  t-r> 

ooccccocccoocccc 

(Ji    OOOOC>--J^^^--'^    COCOOOCK 

coC^^<-"~-J   tyjC   toL^ui^j   coC    t04-    O 
4-    coO    0    0    CO^J    toOui    to    COcnOJ    ^  '^ 
M^lt^4_4_0    M    Oto    cot04-    C    CUi^J 
O'-^O    to    0^-~J-J    ^    "^    C4-    to    CO 

nr"  10  -1                             

0 

Weight 
of  vapor  in  one 

pound  of 
saturated  air. 

n.  to 
c  c 

to 

to 

-u 

-J  4-  ^>o 

0:1  Cj  ^ 

C  w    M 
C   cou) 

to 
to 

4- 

M«CCOCOCCOCOCCO 
C^  M    CO  C>4-  UJtOM«OCOOCC 
HH-jen    toen   toej    O"    coen  eo    to    «    O 
-j^j    coen4-    coo^co^    "    0^44-enO 
C    i-i4_L^— a    Cnm    COO    MOenento 

M    to  <-»0 

4- 

w    «    to  4-     0  0 

i-<    M    toe^4-en    COIO^J    0C4-0 

OCCMen   w   C   t0O4-   to   coe^   ppto 

M 
0 

Weight 

of  dry  air  for 

saturation  with 

one  pound  of 

vapor. 

C  '^ 

C«4;    -^    " 

4- 

„r     -::\oo4-ejen^j  -h   «  co4-  m  m 
cr,OenO    crjCen4-0^    c««eoen4_ 

10   !_0 

^  to 

t>J 

4-  en  ^J 

coo  4- 

OJ 

►I    _,    to  <->o  4 -1    to 

M    M    KH    t0O34-    C^C/OMen    to    too    00 
MenOene.i4-    C    "WOen    Coenoen 
co«4-e^4-4-i-OetentOO    Ctoco 

M 
M 

Cubic  feet 
of  vapor  in  one  po 
of  water 
at  elastic  force 
column  four. 

und 
n 

I-.  ^J 

c« 

C>  to  t^ 

LJ 

b  b  b  b  b  b  b  c  0  c  0  b  b  0  c 

-      -3 

2    o 


cn 


(A     G 


K     > 


M 


w 

> 

> 

7: 

mm 

0 

n 

^ 

0 

36 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


weight  of  pure  vapor  with  air,  which  is  found  to  be   .623  air 

col.  T,  X  col.  4  . ,    ^  1    „ 

I.,  VIZ.,  ^i— ^ 5  X  .023  =  col.  7. 

29.92  I 

Column  8. — Equals  col.  6  -|-  col.  7  =  the  weight  of  one  cubic 
foot  of  saturated  air  at  the  temperatures  in  column  i . 

Column  9. — Shows  the  weight  of  the  vapor  of  water  in  one 
pound  of  a  saturated  mixture  of  air  and  vapor  at  the  tempera- 
tures in  column  i.  It  is  obtained  by  multiplying  the  weight  of 
the  vapor  of  one  cubic  foot  in  column  7,  by  the  volume  of  one 
pound  of  air  at  the  corresponding  temperature,  as  found  in  column 

col    7 
2,  table  XIV.,  or  by  dividing  col.  7  by  col.  6;   — '~  =  col.  9. 

col.  6 

Also,  — '—  =  col.  10,  which  is  the  weight  of  dry  air  required 
col.  7 

to  become  saturated  by  one  pound  of  vapor  at  the  temperatures 

in  column  i . 

Column   I  I. — Represents  the  volume  of  vapor  in  cubic  feet 

from  one  pound  of  water  at  the  elastic  force  in  inches  of  mercury 

in  column  4;  it  is  obtained  by  — '—  =  col.  1 1,  or — '- —  =  col.  1 1. 

col.  7  col.  6 

In  Table  III.  is  shown  the  amount  of  moisture  in  saturated  air 

at  pressures  below  that  of  normal  atmospheric  pressure,  from 

14.7  to  the  zero  of  absolute  pressure,  in  troy  grains  per  cubic 

foot  at  a  temperature  of  60''  F.      It  shows  at  a  glance  the  weight 

of  the  moisture  in  saturated  air  by  the  reduction  of  pressure  to 

a  vacuum. 


TABLE   III.— Absolute  Pressure  Height   of   Barometer    and   Moisture   in 
Saturated  Air  at  60°  F. 


Average 
pressure  to 
square  inch. 

Barometer, 
inches. 

Troy  grains, 
per  cubic  foot. 

Average 
pressure  to 
square  inch. 

Barometer, 

inches. 

Troy  grains, 
per  cubic  foot. 

14.7 

29.922 

5.87 

6.0 

12.213 

2.39 

13 

26.461 

5.19 

5 

10.177 

1.99 

12 

24425 

4-79 

4 

8.142 

1-59 

II 

22.390 

4-39 

3 

6.106 

1. 19 

10 

20.354 

3-99 

2 

4.071 

•79 

9 

18.319 

5-59  ■ 

I 

2.035 

•39 

8 

16.284 

3-14 

0 

0 

.0 

7 

14.248 

2.79 

THE    PHYSICAL   PROPERTIES    OF   AIR, 


37 


In  Table  IV.  is  shown  the  great  increase  in  the  amount  of 
moisture  held  in  saturated  air  in  its  rise  of  temperature  from 
32°  to  94'^  F.     The  weight  is  given  in  troy  grains  to  facilitate 

computation. 

TABLE  IV. — Weight  of  Vapor  in  Ont.  Cubic  Foot  of  Air  When  Satu- 
rated BETWEEN  Temperatures  of  32  F.  and  94  F.  7,000  Troy  Grains 
=  I  Pound  Avoirdupois. 


Temperature 

of  air, 
Fahrenheit. 

Weight, 
Troy  grains. 

Temperature 

of  air, 

Fahrenheit. 

Weight, 
Troy  grains. 

Temperature 

of  air, 

Fahrenheit. 

Weight, 
Troy  grains. 

32 

2.37 

56^' 

5.18 

76° 

9.60 

35 

2.63 

58 

5-51 

78 

10.19 

3S 

2.89 

60 

5.87 

80 

10.  Si 

41 

3-19 

62 

6.25 

82 

11.47 

44 

3-52 

64 

6.65 

84 

12.17 

46 

3-76 

66 

7.08 

86 

12.91 

48 

4.01 

68 

7-53 

88 

13.6S 

50 

4.28 

70 

8.00 

90 

14-50 

52 

4.56 

72 

8.50 

92 

15-33 

54 

4.86 

74 

9.04 

94 

16.22 

For    indicating    the    atmospheric    pressure,    the    mercurial 
barometer  of  standard  make  is  the  onlv  safe  instrument,  but 


Fig.  I.  — aneroid  baromktek. 

for    transportation    and    reconnoissance    the    aneroid   is    easily 
carried  and  is  fairly  reliable. 

Its  disked  and  corrugated  vacuum  chamber  is  attached  to 
the  index  hand  by  levers  through  a  toothed  sector  and  held  in 
position  by  a  spring  for  correcting  adjustment.  The  aneroids 
for  mining  purposes  are  provided  with  a  special  scale  to 
indicate  pressures  from  2,000  or  more  feet  below  sea  level  to 
5,000  or  more  feet  above,  and  are  also  provided  with  a  movable 
vernier  scale  for  levelling. 


38 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


TABLE  V. — Height  ok  Barometer,  Gauge  Pressure,  Boiling  Temperature 
OF  Water,  and  Approximate  Height  in  Feet  Above  the  Level  ok  the 
Sea,  Subject  to  Correction  ok  Barometer  kor  Sea  Level.  Mean  Tem- 
perature OK  Air,  60"  F. 


u 

llT  D     . 

^ 

■~  .s 

0 

a7  0)    • 

*J 

.-     c 

n 

1,  u  ^j: 

.-  i"  X  0 

■~  -'5 

*  0  lU 

*■*  .c  -^ 
agbf  Jj 

<    .= 

1*  -  tl.2 

.?  i  i  i 

ci  C  "U 

.2"  '^ 

ee 

OS 

fe 

30.00 

14-74 

212.2'"' 

0 

22.73 

II. 16 

198.5'^ 

7,250 

29.92 

14.70 

212.0 

70 

22.49 

11.04 

198.0 

7,527 

29.62 

14-55 

211. 5 

333 

22.26 

10.93 

197.5 

7,797 

29-33 

14.40 

211.0 

590 

22.03 

10. 8 1 

197.0 

8,067 

29.04 

14-25 

210.5 

850 

21.80 

10.70 

196.5 

8,342 

28.75 

14. 1 1 

210.0 

1,112 

21  57 

10.59 

196.0 

8,620 

28. 46 

13-97 

209.5 

1,396 

21.35 

10.48 

195-5 

8,887 

28.18 

13-83 

209.0 

1,641 

21.13 

10.37 

195.0 

9,157 

27.89 

13-79 

208.5 

1,905 

20.90 

10.26 

194.5 

9,443 

27.61 

13-55 

208.0 

2,169 

20.68 

10.15 

194.0 

9,719 

27-34 

13-42 

207.5 

2,436 

20.47 

10.05 

193-5 

9,987 

27.06 

13.28 

207.0 

2,688 

20.25 

9-94 

193.0 

10,268 

26.79 

13-15 

206.5 

2,956 

20.04 

9.84 

192-5 

10,541 

26.52 

13.02 

206.0 

3,223 

19.82 

9-73 

192.0 

10,829 

26.25 

12.88 

205.5 

3,488 

19.61 

9-63 

19I-5 

II, loS 

25-99 

12.76 

205.0 

3-752 

ig.41 

9-53 

191. 0 

11,375 

25.72 

12.63 

204.5 

4,022 

19.20 

g.42 

190.5 

11,659 

25.46 

12.50 

204. 0 

4,287 

19.00 

9-33 

190.0 

ii,c33 

25.20 

12.37 

203.5 

+■556 

18.79 

9.22 

189.5 

12,224 

24.94 

12.23 

203.0 

4,827 

18.59 

9.12 

189.0 

12, 503 

24.69 

12.12 

202.5 

5,089 

18.39 

9-03 

188.5 

12,786 

24.44 

12.00 

202.0 

5,357 

18.19 

8.93 

188.0 

13,071 

24.19 

11.88 

201.5 

5,625 

18.00 

8.83 

187-5 

13.346 

23-94 

11-75 

201.0 

5,895 

17.81 

8.74 

187.0 

13,623 

23.69 

11.63 

200.5 

6,168 

17.61 

8.64 

186.5 

13.917 

23-45 

II. 51 

200.0 

6,437 

17.42 

8.55 

186.0 

14,202 

23.21 

11-39 

199-5 

6,706 

17-23 

8.46 

185-5 

14.488 

22.Q7 

11.28 

199.0 

6,976 

17-05 

8.36 

185.0 

14.763 

The  barometric  table  (V.)  is  an  abstract  from  the  physical 
tables  of  the  Smithsonian  Institution,  and  is  approximately 
correct,  an  extension  of  the  decim.als  being  dropped  with  the 
intervening  numbers  for  barometric  height.  The  intervals,  as 
noted,  are  so  nearly  proportional  that  all  the  columns  may  be 
interpolated  between  the  numbers  given  for  any  height  of  the 
barometer  or  boiling-point  of  water.  The  column  of  gauge 
pressure  is  also  convenient  for  reference  when  required.  For 
ascertaining  differences  in  height,  subtract  the  height  due  to 
the  observation  of  the  barometer  at  the  lower  station  from  the 
height  due  to  the  observed  barometer  reading  at  the  upper 
station ;  the  difference  is  the  approximate  height  between  the 


THE    PHYSICAL    PROPERTIES    OF    AIR.  39 

stations.     The  same  is  also  applicable  for  observation  of  the 
temperature  of  boiling  water. 

For  accurate  measurements,  there  are  small  variations  and 
corrections  which  must  be  made  for  difference  of  latitude  from 
45°  and  for  difference  in  temperature  between  the  lower  and 
upper  stations,  and  a  small  correction  for  the  lower  station, 
which  is  only  appreciable  above  i,ooo  feet. 

These  corrections  are  collated  in  all  their  relations  in  the 
valuable  work  of  the  Smithsonian  Institution,  "  Meteoroloeical 
and  Physical  Tables,"  to  which  the  author  refers  for  accurate 
survey  work. 

CONDENSATION    OF    MOISTURE    BY    AIR    COMPRESSION   AND    COOL- 
ING  TO    NORMAL   TEMPERATURE. 

For  any  hygrometric  condition  of  the  atmosphere,  the 
weight  of  water  that  may  be  condensed  by  compression  and 
cooling  the  compressed  air  to  its  normal  temperature  can  be 
approximately  found  by  simply  multiplying  the  value  for 
saturated  air  in  one  cubic  foot,  in  Table  II.,  column  7,  by  the 
hygrometric  percentage,  and  this  product  multiplied  by  the 
number  of  volumes,  less  i. 

Table  VI.  has  been  computed  for  the  temperatures  in  column 
I  by  the  above  formula,  and  as  an  example  for  other  percent- 
ages and  temperatures  than  found  in  the  table ;  say,  for  a 
hygrometric  percentage  of  86  in  free  air,  when  compressed  to  75 
pounds  per  square  inch  from  air  at  an  external  temperature  of 
62^^  F.  ;  we  find  in  column  3,  Table  XL,  at  62",  the  weight  of 
water  in  5  volumes  (6  less  i),  or  cubic  feet,  to  be  .004405  pounds 
per  cubic  foot  of  compressed  air  at  the  point  of  saturation  of  free 
air;  then  .004405  X  86  per  cent  =.0037883  pounds,  which  rep- 
resents the  weight  of  water  that  will  be  precipitated  from  6 
cubic  feet  of  free  air  at  .62"  F.  when  compressed  to  75  pounds 
gauge  pressure  and  cooled  to  normal  temperature.  From  Table 
VI.,  by  interpolation,  the  amount  of  condensation  of  moisture 
may  be  approximately  deduced,   from  the  compression  of  any 


40 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


number  of  cubic  feet  of  free  air  per  minute,  at  any  temperature 
and  pressure,  when  the  compressed  air  is  cooled  to  normal 
temperature. 

TABLE  VI.  — SiiowiNf;  the  Amount  ok  Water  that  may  Condense  in 
Pounds  per  Cubic  Foot  of  COMPRESSED  AIR  at  Various  Pressures, 
WHEN  Cooled  to  Normal  Temperature,  from    SATURATED  Free  Air. 


I 

2 

3 

4 

5 

6 

7 

8 

sed 
lire. 

C    ID 

■J-. 

5  lu 

^^t 

.^.c  1 

<u  ,  cd 

hi 

in   0 

g.5 

.n   c 

0  ° 

0.  S 
0  "  0 

0^  ~ 

2§l 

S   K 

-*   > 

^  > 

V  > 

e^  0  ■' 

^  c  ^ 

o  *! 

p        ^ 

0  0 

^ 

0  "?  ^ 

c   2, 

p-^ 

aS, 

32'  F. 

.000912 

.00152 

.002128 

.004256 

.008816 

.020976 

.045296 

42 

.001320 

.00220 

.003080 

.006160 

.012760 

.030360 

.065560 

52 

.001881 

.003135 

.004389 

.008778 

.018188 

.043263 

•093423 

62 

.002643 

.004405 

.006167 

.012334 

.025549 

.060789 

.131269 

72 

.003663 

.006105 

.008547 

.017094 

•035309 

.084249 

.181929 

82 

.005001 

.008335 

.011669 

.023338 

•04S343 

.115023 

.248383 

92 

.006750 

.011250 

.015750 

. 03 1  500 

.065250 

•155250 

•335250 

The  approximate  percentage  of  Avater  vapor  in  free  air  may 
be  applied  to  the  tabular  figures,  for  the  approximate  weight 
of  condensation  for  any  hygrometric  condition  of  the  atmos- 
phere for  intervals  of  10  degrees  from  32°  to  92°  F.  Barometer 
29.92  inches. 

For  example:  500  cubic  feet  per  minute  at  atmospheric  tem- 
perature of  67°  F.,  compressed  to  75  pounds  per  square  inch. 
Free  air  at  75  per  cent,  of  saturation,  which  is  about  the  mean 
condition  of  the  atmosphere  at  or  near  sea  level.  Omitting  the 
small  increase  in  the  ratio  of  saturation  for  the  rise  in  tempera- 
ture, the  mean  between  62°  and  72°  in  column  3  will  be  found 
to  be  .00525  X  -75  for  the  percentage  of  saturation  =  .0039375  X 
500  cubic  feet  =  1.968  pounds  of  water  condensed  per  minute. 

For  any  other  pressure  than  stated  in  Table  VI.,  use  the 
proportional  difference  between  the  stated  amounts  in  the 
columns  next  to  the  required  pressure  for  the  approximate 
amount  of  condensation  ;  also  the  rule  as  stated  for  any  pressure. 


Chapter  III. 


AIR  IN    MOTION  AND 
ITS    FORCE 


AIR    IN    MOTION    AND    ITS    FORCE. 

The  power  of  air  in  the  force  of  the  wind  was  probably  the 
earliest  of  the  forces  of  nature  captured  by  mankind  and  utilized 
in  moving  the  first  sail  on  the  sea,  and  by  its  progressive  use 
has  contributed  its  vast  power  to  extend  the  civilizing  influence 
of  commerce  to  every  part  of  the  world.  Nor  is  its  power 
confined  to  the  gentle  winds  that  waft  the  sails  or  turn  the 
windmills ;  its  terrors  in  the  storm  and  the  tornado  are  in  con- 
stant evidence. 

In  our  every-day  uses  the  power  of  air  is  what  we  make  it: 
we  compress  it,  we  bottle  it  up  under  vast  pressures,  in  which 
its  power  is  a  potential  element  ready  for  work  at  our  bidding. 

The  force  of  air  in  motion,  the  wind,  was  for  ages  the 
dominant  power,  and  windmills  dotted  the  land  in  all  civilized 
countries.  There  was  a  time  when  the  natural  forces  of  wind 
and  water  were  the  only  ones  at  the  command  of  man  for 
industrial  purposes,  and  when  the  motors  driven  by  these 
forces  monopolized  all  industrial  pursuits  which  man  did  not 
accomplish  by  his  own  physical  exertion.  It  is  still  largely  in 
use,  and  is  probably  the  most  economical  power  available 
within  its  limited  sphere  of  action  ;  it  is  obtainable  in  all  parts 
of  the  world ;  the  wind  blows  over  every  country. 

VELOCITY    AND    PRESSURE    OF    THE    WIND. 

Observations  on  the  velocity  and  pressure  of  the  wind  have 
been  made  under  varying  conditions  as  high  as  159  feet  per 
second,  with  a  pressure  of  57.75  pounds  per  square  foot,  from 
which  it  was  found  that  the  resistance  to  air  in  motion  varied 
as  the  square  of  the  velocity  nearly,  on  surfaces  with  planes  at 
right  angles  to  the  direction  of  the  wind. 


44 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


For  inclined  surfaces  the  resistance  was  found  to  be  1.84th 
power  of  the  sine  X  the  cosine  of  the  angle. 

The  pressure  of  the  wind  varies  slightly  for  given  velocities 
with  its  density  and  temperature;  so  that  with  a  high  baro- 
metric pressure  and  low  temperature,  say  for  above  30  inches, 
the  formula  .005  X  area  X  square  of  the  velocity  in  miles  per 
hour  may  be  used  for  the  pressure  per  square  foot,  or  .0023  X 
area  X  square  of  the  velocity  in  feet  per  second  —  pressure  in 
pounds  per  square  foot. 

For  mean  barometric  pressure  and  temperature  of  35°  F., 
.005  X  the  square  of  the  velocity  in  miles  per  hour  is  in  use, 
and  from  which  the  wind  pressures  in  the  following  table, 
Table  VII.,  have  been  computed.  Also  /v/200  P  =  V.,  in  which 
P  =  pressure  in  pounds  per  square  foot,  and  V  =  velocity  in 
miles  per  hour. 

TABLE   VII. — Velocity    and    Pressure    ok    the    Wind.     At   a    Barometric 
Pressure  ok  29.921  and  Temperature  ok  32^  F. 


Vei.ociiv. 

0 

Observed 

Velocity. 

0 

0 

3  £-« 

t-i      • 

!-       . 

u 

Observed 

<u  0 

+-.  0 
a>  0 

i^  =«  5 

3,   tBiX 

character  of  the 
wind. 

0!   3 

<U  0 

*j  0 

« s  § 

character  of  the 
wind. 

^  ^ 

!l>'^ 

a>  ^ 

u 

^  i" 

0/    r- 

D  m 

u 

a. 

cZS 

fe« 

p. 

I  '^- 

fc  =« 

<u 

I 

88 

r-47 

0.005 

Barely  observed. 

16 

1,408 

23.48 

1. 29 1 

2 

176 

2.93 

.020 

Just  perceptible. 

17 

1,496 

24-93 

1.458 

3 

264 

4.40 

.045 

Very  light. 

18 

1,584 

26.40 

1.634 

4 

352 

5.87 

.081 

Light  breeze. 

19 

1.672 

27.86 

1. 821 

5 

440 

7-33 

.126 

Fair  breeze. 

20 

I,    760 

29.33 

2.018 

6 

528 

8.  So 

.iSi 

Verj'  fair  breeze. 

25 

2,200 

36.67 

3.155 

Very  brisk. 

7 

616 

10.27 

.247 

30 

2,640 

44.00 

4-547 

[  High  wind. 

8 

704 

"•73 

.323 

Fresh  breeze. 

35 

3,080 

51.33 

6.194 

9 

792 

13.  2D 

.408 

40  3,520 

58.67 

8.099 

Very  high  \vind. 

10 

S80 

14.67 

•  505 

Strong  breeze. 

45   3.960 

66.00 

10.260 

Gale. 

II 

968 

16.  13 

.610 

50|  4,400 

73.33 

12.684 

Storm. 

12 

1,056 

17.60 

.726 

60   5,280 

88.00 

18.310 

Great  storm. 

13 

1,144 

19.07 

.S52 

80   7,040 

II7-3 

32.80 

Hurricane. 

14 

1,296 

20.53 

.988 

90   7,920 

132.0 

40.50 

[  Tornado. 

15 

1,320 

22.00 

1. 135 

Stiflf  breeze. 

100 

8,800 

146.6 

50.00 

There  is  a  variation  in  pressure,  due  to  temperature, 
amounting  to  about  1.7  per  cent  of  the  tabulated  pressures, 
which  are  additive  below  32°  F.,  and  subtractive  above,  for 
each  10°  F;  so  that  in  a  hurricane  at  80  miles  an  hour,  with  the 


AIR    IN    MOTION    AND    ITS    FORCE.  45 

thermometer  at  90^,  the  pressure  would  be  29.16  pounds  per 
square  foot,  instead  of  32.8  in  the  table. 

The  wind  pressure  on  spherical  surfaces  is  approximately 
0.36,  that  on  a  plane  circular  surface  of  the  same  diameter,  as 
in  Fig.  2.     On  a  cylindrical  surface  of  a  length 
equal  to  its  diameter  the  wind  pressure  is  equal  f 

to  0.5  that  on  a  plane  surface  equal  to  the  diame- 
ter and  length  of  the  C3'linder ;  hence  the  power 
that  operates  the  cupped  or  curved  blade  ane- 
mometers and  horizontal  windmills.  The  curved 
blades,  as  shown  in  Fig.  3,  represent  the  prin-  ^van k  wTn^umiIl!' 
ciple  of  the  action  of  the  wind  on  curved  surfaces. 
As  a  windmill,  this  form,  as  well  as  mills  made  with  flat,  in- 
clined blades  revolving  on  a  vertical  axis,  are  very  much  weaker 
in  power  than  the  vertical  plane  form,  as  shown  in  Fig.  5, 
which  has  been  found  to  possess  a  higher  efficiency  than  any 
of  the  windmills  of  other  forms. 

The  measurement  of  the  velocity  and  force  of  the  wind  is 

approximately  obtained  by  the  use  of  anemometers  of  various 

kinds  for  the  velocity  and  by  resistance  planes  for  its  force. 

The  Robinson  four-armed  cup  form,  used  by  the  United  vStates 

Weather  Bureau,  is  generally  accepted  as  the  best  form  for  a 

I  stationary  anemometer.     The  small   Davis  or 

i  Biram  windmill  anemometers,  with  gear  and 

/^OkQtG  ^^^^^  adjusted  for  indicating  the  velocity  of  air 

Q>  (>?        currents  in  mines  or  ventilating  passages,  are 

^     M     'It-'       much  in  use  and  fairlv  reliable. 

c)^r^  With  the  cup  anemometer  the  experiments 

FIG.  3.-ANEM0M-     of  Dr.  Robinson  and  others  on  the  difference 


ETER. 


in  force  of  the  wind  upon  the  spherical  and 
hollow  side  of  a  cup  resulted  in  finding  that  the  pressure  for 
all  wind  velocities  was  four  times  as  much  on  the  concave  side 
as  upon  the  convex  side. 

By    differentiating    the    pressures,    it   was    found    that   the 
velocity  of  the  wind  was  about  three  times  the  velocity  of  the 


46 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


Fig.  4.— ROBINSON'S  ANEMOMETEU. 


centre  of  the  cups,  not  including  the  friction,  which  is  a 
variable  factor  to  a  small  extent,  slightly  increasing  with 
the  velocity  of  the  wind.  The  ratio  for  the  differential 
pressure   and   friction   in   the  standard  cup  anemometers  of  4 

inches  cup  diameter  and  7-inch  ra- 
dius to  their  centres,  is  3,  from 
which  their  dial  gear  is  computed. 

In  Fig.  4  is  shown  the  general 
construction  and  arrangement  of 
the  index  train  of  a  Robinson  ane- 
mometer. Each  dial  is  graduated 
respectively  to  o.  i  mile,  i  mile,  10 
miles,  100  miles,  1,000  miles,  and 
these  revolve  behind  fixed  indexes, 
the  readings  of  which  are  taken  according  to  the  indication  on 
the  faces  under  the  indexes.  Observations  are  recorded  by  dif- 
ferentiating the  readings  of  the  dials  and  multiplying  by  the 
observed  time.  A  most  convenient  way  is  to  record  the  read- 
ings of  the  dials  at  intervals  of  12  minutes  and  divide  their 
difference  by  10  for  the  velocity  of  the  wind  in  miles  per  hour. 
The  Biram  anemometer  (Fig.  5)  is  much  in  use  for  testing 
the  velocity  of  the  air  current  in  the  ven- 
tilation of  mines,  hospitals,  schools,  and 
public  buildings. 

For  testing  the  volume  of  air  passing 
in  a  ventilating  flue  or  air-shaft  of  a  mine, 
select  a  place  having  a  uniform  section ; 
let  the  instrument  run  a  short  time  to 
gain  full  speed  ;  then  test  it  one  minute  by 
a  watch  and  note  the  velocity,  as  indicated 
by  the  difference  of  the  two  dial  readings 

at  the  beginning  and  end  of  a  minute;  then  multiply  the  area 
of  the  flue  or  air-shaft  in  square  feet  by  the  velocity  in  feet 
per  minute  for  the  cubic  feet  per  minute.  In  some  of  the 
States  the  law  requires  a  supply  of    100  cubic   feet  of  air  per 


Fig. 


BIRAM      ANEMOM- 

F.TER. 


AIR    IN    MOTION   AND    ITS    FORCE. 


47 


man    per   minute,  and  as  much  more  as  the  special  condition  of 
the  mine  may  require. 

The  direct  pressure  of  air  currents  up  to  about  6  inches  for 
water,  or  -jVof  ^^  ^  pound  per  square  inch,  and  indicating 
velocities  up  to  near  80  miles  per  hour,  is  readily  obtained  by 
Lind's  siphon  pressure  gauge,  shown  in  Fig.  6.  It  consists 
of  a  glass  siphon,  with  parallel  limbs,  mounted  upon  a  vertical 
rod,  on  which  it  moves  freely  by  the  action  of  the  vane  which 
surmounts  it.  The  upper  part  of  one  of  the  limbs  is  bent  out- 
ward toward  the  wind.  Between  the  limbs  is  a  graduated 
scale,  indicating  from  o  to  3  inches  in 
loths,  the  zero  being  in  the  centre  of 
the  scale.  In  use,  the  tube  is  filled 
with  water  to  the  zero  of  the  scale  and 
exposed  to  the  action  of  the  wind,  b}' 
which  the  water  is  depressed  in  the 
one  limb  and  raised  in  the  other. 
The  sum  of  the  elevation  and  depres- 
sion is  the  height  of  the  column  which 
the  wind  is  capable  of  sustaining. 

The  pressure  indicated  is  .036  of 
a  pound  per  square  inch  per  inch  of 
difference  in  the  level  of  the  two  legs 
of  the  siphon,  or  5.18  pounds  per  square  foot.  Then  each 
division  of  one-tenth  of  an  inch  will  represent  .518  of  a  pound 
per  square  foot,  and  by  reference  to  the  wind-pressure  column 
in  Table  VII.  the  approximate  velocity  of  the  wind  for  any 
pressure  may  be  found.  This  also  corresponds  with  the  veloci- 
ties derived  from  water  pressure  in  Table  X. 

The  capacity  of  air  for  evaporating  water  varies  greatly, 
depending  upon  the  temperature  of  the  water,  the  relative 
temperature  of  the  air,  its  humidity,  and  its  velocity  over 
the  surface.  These  four  conditions  vary  the  effect  one  with 
another,  so  that  from  the  following  table  of  observed  evapora- 
tion   for    even    temperatures  of   both    air  and   water   and    for 


Fig.   6.— the    siphon     pressure 

GAUGE. 


48 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


degrees  of  humidity  by  tenths,  a  fair  estimate  may  be  made  for 
different  conditions: 


TABLED    VIII. — EvAroKATioN    at    Even    TEMi'KKATrRES    of    Water    and    Air 

AND     AT     DiFFftRENT     STATES      OK     HlMIDITV      OK      THE      AlK,       IN      GRAINS      I'ER 

Square  Foot  per  Hour,   in  Calm  Air.  (Box.) 


Tempera- 

Hi'MIDITV  OF  THE  AlR  ;  SATURATION  =  100. 

of  air  and 
water. 

Dry. 

30 

40 

50 

60 

70 

80 

90 

32°  F. 

42 

52 

62 

72 

82 

92 

69 

lOT 

147 
211 
298 
426 
570 

48 

71 

103 
148 
209 
298 
400 

41 
61 

88 
127 
178 
256 
342 

34 

51 

74 

106 

149 
213 

285 

28 

40 

59 

84 

119 

170 

228 

21 
30 
44 
63 
89 
12S 
171 

14 
20 
29 
42 
60 
85 
114 

7 
10 

15 
21 
30 
43 

57 

From  experiments  by  Dr.  Dalton,  the  increase  of  evapora- 
tion from  a  calm  by  a  light  wind  of  three  or  four  miles  per 
hour  made  an  increase  in  the  evaporation  of  28  per  cent,  and 
from  a  fresh  breeze  of  about  8  miles  per  hour  made  an  increase 
of  evaporation  of  50  per  cent  for  air  of  nearly  the  same  tem- 
perature of  the  water.  A  warmer  wind  than  the  water  will 
somewhat  increase  the  evaporation  and  a  colder  wind  will 
retard  it. 


Chapter   IV. 


AIR  PRESSURES 

BELOW 

ATMOSPHERIC  PRESSURE 


AIR  PRESvSURES  BELOW   ATMOSPHERIC   PRESSURE. 

A  VACUUM  is  the  zero  of  atmospheric  pressure,  and  is  the 
beginning  from  which  the  absolute  pressures  start  in  many  air 
problems;  and,  like  the  absolute  zero  of  temperature,  it  is  the 
point  in  the  scale  of  pressure  at  which  air  expansion  becomes 
infinite,  and  to  which  temperatures  contract  to  the  measure  of 
interplanetary  space. 

One  of  the  means  by  which  the  pressure  of  the  atmosphere 
is  reduced  toward  a  vacuum  is  an  air  pump  (Fig.  7).  Its 
power  to  produce  negative  atmospheric  pressures  to  a  certain 
extent  is  complete;  but  is  limited  in  idtimate  results  by  the 
amount  of  the  volume  of  clearance  divided  by  the  volume  of 
the  piston  stroke. 

At  the  point  of  the  greatest  exhaustion  by  an  air  pump  the 
clearance  volume  expands  by  its  elasticity  as  the  piston  recedes 
and  fills  the  entire  cylindrical  space,  so  that  the  best  mechanical 
pump  can  scarcely  produce  a  vacuum  of  less  than  one-hundredth 
of  an  inch  of  mercury,  and  often  one-tenth  of  an  inch  is  the 
limit.  Referring  to  the  cut,  the  pump  consists  of  two  cylinders 
with  pistons  operated  by  racks  on  each  side  of  a  pinion  and  the 
oscillating  motion  of  the  handles  M  N.  Each  piston  has  a 
valve  opening  upward,  and  the  base  of  the  cylinder  also  has  a 
valve  opening  upward  at  c\  the  cock  at  O  is  to  shut  off  one  of 
the  cylinders,  and  a  cock  at  .V  shuts  off  both  cylinders  to 
prevent  leakage;  r  is  a  relief  valve.  At  7"  is  a  cock  to  shut  off 
the  mercury  gauge  E,  which  is  a  U-shaped  glass  tube  with  one 
end  closed  and  the  tube  partly  filled  with  mercury,  and  with  a 
Torricellian  vacuum  in  the  closed  end,  and  a  gauge  attached; 
the  whole  enclosed  in  a  glass  cover  and  connected  with  the 
cock   T.     The  platform    V  is  arranged  to  seal   by  contact  the 


52 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


various  implements  used  in  experimenting  on  the  properties  of 
air  below  atmospheric  pressure. 

The  hydraulic  air  ejector,  Venturi  vacuum  pump,  or  aspi- 
rator, is  a  most  convenient  instrument  for  quickly  obtaining  an 
approximate  vacuum.  In  its  construction  the  form  of  the. 
curved  nozzles  is  made  after  the  suggestions  first  enunciated 
by  Venturi,  on  the  principle  that  a  passing  fluid  at  a  high 
velocity  through  a  converging  and  a  diverging  nozzle,  in  which 


Fig.   7.-THK   AIR   PUMP. 

the  curves  conform  to  the  shape  of  the  I'cna  contracta  of  a  jet 
from  an  orifice,  will  produce  an  approximate  vacuum  at  a  point 
near  its  greatest  contraction,  and  if  an  air  chamber  is  connected 
through  an  orifice  at  this  point,  the  air  will  be  discharged  and 
nearly  a  perfect  vacuum  will  be  made  in  the  air  chamber.  The 
water-entering  nozzle  may  be  connected  by  a  rubber  tube  to 
any  faucet  of  a  town  water-works,  or  from  a  tank  having  a  head 
of  more  than  14  feet,  or  one-half  the  static  water-head  of  a 
vacuum.  The  air-inlet  leg  requires  an  elastic  valve,  as  shown 
in  the  cut,  and  a  small  bar  occupying  nearly  one-half  the  area 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  53 

of  the  water-exit  end  has  been  found  necessary  in  practice  for 
its  more  perfect  action.  The  cut  is  an  exact  proportional  form 
and  one-half  the  dimensions  of  those  in  use  in  laboratory  and 
experimental  work.  It  is  capable  of  producing  a  vacuum  equal 
to  the  barometric  height,  less  the  height  due  to  the  tension  of 
the  vapor  of  water,  which  at  60°  F.  equals  one-half  inch  of 
mercury ;  while  at  the  temperature  of  the  greatest  density  of 
water,  a  vacuum  ranging  within  one-quarter  of  an  inch  of  the 
barometric  height  due  to  the  atmospheric  pressure  may  be 
obtained. 

The  aspirator  for  various  purposes  has  been  made  in  several 
forms,  following  the  principles  of  the  hydraulic  ejector  and  the 
steam  injector  for  large  volumes;  but  for  general  utility,  this 
simple  form  has  come  into  use  for 
experimental  work  in   educational 
institutions,  and  in  the  arts  where 
an  automatic  and  constant  vacuum 
draft  is  needed.     The  aspirator  is 
made  by  ]Mr.  E.  C.  Chapman,  287 
Gates  Avenue,  Brookhm,  N.  Y. 

For  a  more  perfect  vacuum  than  p^^  s.-venturi  vacuum  pump. 
the  air  pump  or  the  hydraulic  aspi- 
rator gives,  the  Sprengel  mercurial  air  pump  is  found  to  produce 
nearly  a  Torricellian  vacuum.  One  of  the  many  forms  of  this 
pump  we  illustrate  in  Fig.  9,  which  can  be  readily  constructed 
by  any  amateur  of  ordinary  genius.  The  individual  tubes  are 
shown  in  the  section  to  the  right  of  the  assembled  instrument. 

The  materials  necessary  for  the  construction  are  as  follows : 
A  piece  of  soft  glass  tubing  5  ft.  long,  with  a  bore  of  about  |  of 
an  inch  (i  centimetre);  three  pieces,  each  5  ft.  long,  with  a 
bore  of  Jg  of  an  inch,  having  fairly  thick  walls,  say  -^  of  an 
inch.  If  the  bore  is  much  over  -^  of  an  inch,  the  pump  will 
not  produce  a  good  vacuum.  Two  or  three  feet  of  thick  rubber 
hose  to  connect  the  pump  with  the  vessel  to  be  exhausted ;  a 
quart  bottle,  with  the  bottom  cut  off,  and  a  brass  screw  clamp. 


54 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


The  large  tube  is  to  be  drawn  down  to  half  its  diameter 
about  an  inch  frcMii  one  end.  The  bore  of  this  contracted 
portion  should  be  too  narrow  to  admit  one  of  the  smaller  tubes. 
This  allows  of  a  cement  joint  of  good  sealing-wax,  or  a  mix- 
ture of  pitch  and  gutta-percha.  The  exhaust  tube  E  should  be 
joined  to  the  T' bend  at  B  by  welding  the  glass.     The  clip  on 

the  rubber  connecting-piece  at  D  serves 
to  regulate  the  flow  of  the  mercury- 
through  the  small  tube  within  the  large 
tube,  and  which  should  extend  about 
2    inches   below   the   scale.      The   lono- 

o 

leg  of  the  large  tube  may  be  36  inches 
in  length.  The  U  bend  at  B  should 
be  on  a  level  with  the  zero  mark  on 
the  inverted  30-inch  scale.  A  small 
cup  seals  the  end  of  the  small  tube  at 
G.  The  overflow  of  mercury  falling 
into  the  receptacle  below,  allows  of  its 
transfer  to  the  bottle  above  through  a 
funnel  and  filter  of  paper  perforated 
at  the  bottom.  The  apparatus  ma}'  be 
arranged  on  a  board  and  the  whole  ap- 
portioned by  the  inch  scale,  as  shown 
in  the  figure.  R  represents  the  attach- 
ment of  a  radiometer  or  an  incandes- 
cent lamp,  and  /^that  of  a  Geissler  tube. 
To  run  the  apparatus  a  good-sized  cup 
of  mercury  will  be  required.  The  more  mercury  there  is  the 
less  trouble  there  will  be  in  continually  transferring  it  from 
the  basin  to  the  reservoir.  Close  the  clamp  first,  also  stop  the 
exhaust  tube  at  E,  then  pour  the  mercury  into  the  funnel.  It 
will  run  through  in  a  few  minutes,  leaving  a  black  scum  on 
the  paper  imless  pure.  Now  open  the  cock  a  little  and  the 
tubes  begin  to  fill,  the  fluid  rising  in  a  double  column  in  the 
large  and  small  tubes.     As  soon  as  it  reaches  the  7"  it  will  flow 


Fig.  9.— mercuriai.  air  pumh. 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  55 

over  and  down,  dragging  air  from  the  exhaust  tube.  Stop  the 
flow.  You  will  notice  that  the  column  in  the  large  open  tube 
does  not  rise  above  the  T ;  hence  it  cannot  overflow.  Make  a 
paper  scale,  divided  into  30  inches,  and  duly  marked;  paste 
this  beside  the  large  tube,  so  that  the  top  of  the  scale  is  oppo- 
site the  top  of  the  mercurial  column.  Everything  is  now  ready 
for  the  process  of  exhaustion.  Connect  the  exhaust  tube  with 
the  vessel  (say  a  Geissler  tube,  F)  by  means  of  a  piece  of  rubber 
tube,  which  should  fit  rcry  tiglitly  over  the  tubes.  Open  the 
clip  a  little  and  the  drops  of  mercury  immediately  begin  to 
tumble  over  the  bend  and  go  chasing  each  other  down  the  long 
tube.  They  should  go  over  quite  slowly,  say  two  a  second,  and 
the  spaces  between  them  will  be  quite  long  at  first.  Notice 
the  mercury  column  in  the  large  tube;  it  is  falling  rapidh',  and 
by  observing  the  scale  you  may  know  exactly  how  the  exhaus- 
tion is  proceeding.  When  the  column  reaches  the  15-inch 
mark,  exactly  one-half  of  the  air  has  been  removed  from  the 
vessel.  As  the  exhaustion  proceeds,  the  air  between  the 
falling  drops  becomes  thinner  and  thinner,  and  finally  we  have 
a  solid  column  in  the  long  tube,  standing  30  inches  above  the 
surface  of  the  cup  G,  upon  which  the  drops  fall  with  a  sharp 
metallic  click,  and  the  column  of  mercury  in  the  large  tube 
will  stand  at  the  index  of  the  barometric  pressure.  This  ham- 
mering of  the  pump  shows  that  the  exhaustion  is  very  perfect, 
the  air  being  too  thin  to  serve  as  an  elastic  cushion.  The 
pump  should  be  allowed  to  hammer  away  for  a  few  minutes, 
when  the  vessel  may  be  disconnected,  either  by  fusing  the 
glass  tube  connecting  it  with  the  hose  or  in  any  way  that  is 
desired.  Care  must  be  taken  to  keep  the  reservoir  supplied  by 
transferring  the  mercury  from  the  basin  to  it.  It  is  best  to 
have  two  basins,  and  exchange  them  at  intervals.  With  this 
pump,  Geissler  and  Plucker  tubes,  or  small  electric  light  bulbs, 
may  be  exhausted,  and  any  experiments  requiring  high  vacua 
may  be  performed.  A  vacuum  of  3-00,000.000  o^  ^"  atmosphere 
is  claimed  to  have  been  made  with  this  form  of  Sprengel  pump. 


56 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


The  general  principles  of  the  combined  condenser  and  air 
pump  are  shown  in  Fig.  lo,  in  which  A  is  the  exhaust  inlet  to 
the  condenser  F,  B  the  water  inlet,  and  D  the  spray  valve, 
which  is  adjusted  by  the  valve  wheel  on  the  valve  spindle  at 
E,  G  the  pump  piston,  H  the  suction  valves,  and  /  discharge 
valves;   A',  steam  chest  and  valve. 

In  this  class  of  injector  condensers,  from  27  to  30  times  the 
weight  of  steam  used  in  the  engine  must  be  furnished  in  water 
to  the  condenser.  For  instance,  if  an  engine  is  using  20 
pounds  of  steam  per  horse-power  per  hour,  then    540  or  more 

pounds  of  water,  or  72  or  more 
gallons  of  water  per  hour,  must 
be  provided  for  effectual  con- 
densation. The  capacity  of  the 
air  pump  should  exceed  the 
water  volume  by  about  50  per 
cent  for  effectual  work  and  for 
maintaining  a  vacuum  of  24  to 
26  inches  of  inercury. 

The  steam  vacuum  or  air 
pumps,  as  now  constructed,  of 
which  Fig.  1 1  is  a  representa- 
tive air  pump  and  jet  conden- 
ser, made  by  Guild  &  Garrison,  and  Fig,  12  is  a  vacuum  pump  for 
the  work  of  evaporation  in  vacuum  pans,  enables  the  produc- 
tion of  a  vacuum  within  one  inch  of  the  barometric  height,  and 
will  maintain  a  vacuum  of  two  inches  less  than  the  barometric 
height  for  steam  power  with  a  good  condenser. 

For  evaporating  and  concentrating  liquids  and  syrups,  there 
is  a  considerable  range  in  the  amount  of  water  that  can  be 
evaporated  from  various  kinds  of  liquids  and  substances,  owing 
to  their  degree  of  viscosity,  which  property  seems  to  have  a 
holding  power  on  the  water  with  which  they  are  combined  or 
saturated.  The  evaporation  of  natural  water  at  normal  tem- 
peratures   under    reduced     atmospheric    pressure    is     largely 


Fig.  10.— coNPEisfSER  and  pump. 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE. 


57 


increased  from  the  conditions  and  temperatures  shown  in  Table 
VIII.  for  open-air  evaporation. 

The  experiments  of  Daniel!  show  that  the  evaporation  of 


Fig.  II.— guild  &  garrison  air  pump  and  jet  condenser. 


water  is  nearly  inversely  proportioned  to  the  pressure,  so  that 
at  half  the  normal  pressure  the  evaporation  would  be  doubled. 
With  a  vacuum  as  nearly  perfect  as  could  be  obtained,  or  ^^j 
of  a  normal  barometric  pressure,  the  evaporation  is  increased 


58  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

about  70  times  more  than  would  be  due  to  the  evaporation  at 
normal  atmospheric  pressure. 

Referring  to  Table  VIII.  as  a  gauge  for  open-air  evaporation, 


471 


Fig.  12.— vertical  double-acting  air  pump  and  jet  condenser. 
One  of  several  types  built  by  the  Dean  Brothers  Steam  Pump  Works,  Indianapolis,  Ind. 

and  using  the  third  column  as  representing  the  conditions  at 
one-half  atmospheric  pressure,  or  barometer  at  15  inches,  tem- 
perature 62°,  we  would  have  an  evaporating  effect  of  296  grains 
of  water  per  square  foot  of  surface  per  hour.     The  distillation 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE. 


59 


of  water  at  higher  temperatures  and  under  a  higher  vacuum 
with  a  surface  condenser  is  a  most  important  item  in  the  pro- 
duction of  artificial  ice,  and  by  reducing  the  vacuum  to  |,j  and 
heating  the  water  to  its  boiling-point  under  the  vacuum,  say 
I  14°  F.,  from  8  to  10  pounds  of  water  may  be  evaporated  per 
square  foot  of  surface  per  hour. 

TABLE  IX. — Boiling  amj  Vapokizinc  Temi-eratukes  ok  Water,  At  and 
Below  Atmospheric  Pressure,  with  Pressures  and  the  Volume  of  One 
Pound  of  Vapor.  (Claudel.) 


Pressure. 

Volume  of 

Tempera- 

Pressure. 

Tempera- 

Volume of 

ture, 

Per 

one  pound, 

ture, 

Per 

one  pound. 

Fail. 

Jlercnry, 

square 

cubic  feet. 

Fah. 

Mercury, 

square 

cubic  feet. 

inches. 

inch, 
pounds 

inches. 

inch, 
povinds. 

211' 

29.92 

14.70 

27.2 

120' 

3-43 

1. 68 

204.9 

210 

28.75 

14.12 

28.2 

"5 

2-97 

1.46 

234-7 

205 

25-99 

12.77 

31.0 

no 

2-57 

1.27 

268.1 

200 

23.46 

ir.52 

34-1 

105 

2.23 

1.09 

307-7 

195 

21.14 

10.38 

37-6 

100 

1. 91 

-94 

353-4 

190 

19.00 

9-33 

41-5 

95 

1.64 

.81 

40S.2 

185 

17.04 

8-37 

45-9 

90 

1. 41 

.69 

471-7 

180 

15-29 

7-51 

50.8 

85 

1.20 

-59 

549-5 

175 

13-65 

6.71 

56.4 

80 

1.02 

-50 

641.0 

170 

I2.l8 

5-98 

62.4 

75 

-87 

-43 

746.3 

165 

10.84 

5-33 

69.8 

70 

•73 

-36 

877.2 

160 

9-63 

4.73 

75.0 

65 

.62 

-30 

1031.0 

155 

8-53 

4.19 

87.3 

60 

-51 

-25 

1220.0 

150 

7-55 

3-71 

97-8 

55 

■  42 

.21 

1429.0 

145 

6.66 

3-27 

IIO.O 

50 

.36 

.18 

1695.0 

140 

5.86 

2.88 

124. 1 

45 

•30 

-15 

2041.0 

135 

5-17 

2.54 

140. 1 

40 

.25 

.12 

2439.0 

130 

4-51 

2.21 

158.7 

35 

.20 

.10 

2941.0 

125 

3-93 

1-93 

180.5 

32 

.iS 

.09 

3226.0 

The  steam  or  other  power  vacuum  pump  is  the  means  of 
utilizing  the  work  from  a  vacuum  for  commercial  purposes. 

Their  use  is  a  source  of  economy  in  all  operations  requiring 
a  large  amount  of  air  to  be  withdrawn  from  an  e\'aporating 
apparatus  or  to  keep  up  the  greatest  tension  possible  when  a 
large  quantity  of  water  is  used  for  conden.sation,  as  it  has  been 
shown  in  previous  chapters  that  water  in  its  natural  condition 
holds  a  considerable  amount  of  air,  which  becomes  liberated 
under  a  vacuum ;  hence  the  necessity  of  the  use  of  a  large 
vacuum  pump  where  jet  condensation  is  used. 

In  Fig.  13  is  shown  a  vacuum  pump  of  the  Guild  &  Garrison 
type,  much   used   in    operating  the  triple   effect  sugar  trains.' 


6o 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE. 


6l 


The  large  air  head  on  this  class  of  pumps  is  for  the  purpose  of 
arranging  the  inlet  and  outlet  valves  above  the  cylinder,  and 
to  allow  the  clearance  to  be  charged  with  solid  water  and  to 
retain  it,  so  that  there  shall  be  a  perfect  exit  of  the  air  above 
the  water.  To  prevent  shock  by  the  water  striking  a  level 
valve  plate  and  to  leave  no  space  that  can  retain  air,  the  exit- 


FlG.    14.— VACUUM  PUMP  CHAMBI  R. 


valve  plate  is  placed  in  an  inclined  position,  as  shown  in  Fig. 
14,  which  allows  every  fraction  of  space  to  be  closed  by  the 
clearance  water  at  the  end  of  each  stroke  of  the  pump. 

In  the  "wet  system"  all  the  water  used  for  condensation 
passes  through  the  pump,  while  in  the  "dry  system"  the 
barometrical  column,  or  leg  pipe,  carries  off  the  injection  water 
by  gravity  from  the   bottom  of  the  condenser  without  passing 


62 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  6^ 

through  the  pump.  The  combined  vacuum  and  water  pumps 
are  so  arranged  that  when  connected  with  a  vacuum  pan  work- 
ing on  the  "  dry  "  system,  the  water  cylinder  of  the  pump  is 
connected  to  deliver  the  injection  water  to  the  tank  that  feeds 
the  condenser,  or,  if  preferred,  to  the  condenser  direct.  In 
Cuba  and  other  places  where  the  "cooling  tower"  is  in  vogue 
(the  injection  water  being  used  over  and  over  again),  the  water 
cylinder  is  arranged  to  take  the  warm  water  discharged  by  the 


FIG.   i6.— CI-AYTON  STEAM   ACTUATED   VACUUM    PUMP. 

air  cylinder  and  deliver  it  to  the  "cooling  tower."  This  is  the 
general  arrangement  when  working  on  the  "wet"  system. 

Fig.  1 6  represents  the  duplex  vacuum  pumip  of  the  Clayton 
Air  Compressor  Works,  New  York  City,  in  sizes  ranging  from 
4-inch  to  1 6-inch  diameter  of  vacuum  cylinder,  with  corre- 
sponding steam  cylinders  of  less  size ;  stroke  from  3  to  1 5 
inches.  They  are  constructed  with  water- jacketed  vacuum 
cylinders  when  desired. 

Poppet  valves  are  placed  in  the  heads  of  the  cylinders. 
Single  vacuum  pumps  are  made  of  the  same  sizes. 

The  Blake  duplex  fly-wheel  vacuum  pump  is  illustrated  in 


64  COMrKESSEl)    AIR   AND    ITS    APPLICATIONS. 

Fig.  17,  in  which  the  design  of  tlie  vacuum  cylinder  and  valves 
is  such  that  the  same  pump  may  be  used  equally  well  for  the 
wet  or  dry  system  of  evaporation. 

THE  COMMERCIAL  UTILITY  OF  A  VACUUM. 

The  history  of  the  vacuum  in  the  United  wStates  Patent 
Office  is  an  interesting  one,  dating  back  to  1833,  in  which  year 
George  H.  Richards  took  out  exclusive  rights  in  a  process  for 
preparing  leather  from  various  substances  by  evaporation  in 
vacuo  at  a  temperature  below  212°,  the  object  being  to  avoid 
injuring  the  product  by  too  great  heat.  This  method  is 
applied  in  obtaining  flavors  for  sirups  dispensed  at  soda-water 
fountains.  It  also  serves  in  making  extracts  from  malt  and 
hops  and  from  coffee.  The  fact  is  well  known  that  firms 
engaged  in  the  business  of  roasting  coffee  for  market  commonly 
deprive  the  beans  of  their  volatile  flavoring  essence  and  sell  the 
latter  separately.  An  honest  coffee  roaster  returns  this  essence 
to  the  beans.  ]\Iuch  of  it  passes  off  during  the  ordinary  cook- 
ing process,  and  thus  it  happens  that  at  times  the  streets  in  the 
neighborhood  of  a  coffee-roasting  store  are  fragrant  with  the 
odor  of  coffee.  It  is  agreeable  to  the  nostrils,  but  very  waste- 
ful. A  properly  constructed  roasting-machine  saves  and  con- 
denses the  vapor. 

Bakers  use  great  quantities  of  egg  meats  dried  in  vacuum 
pans.  The  eggs  are  broken  into  the  pans,  the  whites  and 
yolks  being  separated.  They  are  then  evaporated  to  dryness, 
after  which  they  are  scraped  from  the  pans  and  granulated  by 
grinding.  The  product  looks  very  much  like  sawdust;  it  is 
comparatively  cheap,  and  will  keep  good  for  many  months, 
taking  the  place  of  fresh  eggs  when  the  latter  are  scarce  and 
dear.  A  similar  process  is  employed  in  the  manufacture  of 
so-called  "egg  albumen,"  which  is  said  to  be  composed  largely 
of  the  whites  of  eggs.  It  looks  like  a  fine  quality  of  glue, 
being  used  by  bakers  and  for  glazing. 


AIR    PRESSURES    BELOW   ATMOSPHERIC    PRESSURE. 


65 


Several  processes  have  been  patented  for  preserving  eggs 
in  their  shells  by  means  of  the  vacuum.  One  method  is  to  place 
them  in  a  chamber,  which  is  then  exhausted  of  air.     The  air, 


>.       al 


I    z 


containing  the  germ  of  decomposition,  is  thus  drawn  out  of  the 
eggs,  and  carbonic  acid  gas  is  forced  into  the  receiver  to  take 
the  place  of  it.  A  variation  of  this  idea  is  to  introduce  into  the 
receiver  melted  paraffine,  which  fills  the  pores  of  the  shells. 

5 


66  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

Eggs  are  canned  by  the  vacuum  process,  being  heated  some- 
what to  preserve  them,  but  the  temperature  to  which  they  are 
rased  cannot  be  high,  for  the  white  hardens  at  140°  F. 

There  are  numerous  patents  for  preserving  foods  with  the 
aid  of  the  vacuum.  One  idea  is  to  extract  the  air  contained  in 
the  meat,  fish,  and  fruit,  which  are  to  be  impregnated  there- 
upon with  a  solution  of  gelatine.  This  being  accomplished, 
the  meat  is  to  be  taken  and  dipped  into  a  solution  of  gelatine, 
sugar,  and  gum,  so  as  to  give  it  a  coating  on  the  outside. 
Thus  it  will  keep  for  an  indefinite  period. 

Vacuum  processes  are  to-day  largely  and  successfully 
employed  in  the  salting  and  pickling  of  meats  and  vegetables. 
They  are  shut  up  in  chambers  from  which  the  air  is  withdrawn, 
and  brine  is  then  forced  in  under  pressure.  The  meat  is  some- 
times stuck  full  of  tubular  perforated  skewers,  to  permit  the 
gases  to  escape  and  to  admit  the  brine  to  all  parts  of  the 
substance  treated.  Another  method  adopted  is  to  withdraw 
the  brine  with  the  air  pump  and  force  smoke  into  the  meat, 
which  is  thus  smoked  as  well  as  salted.  On  this  idea  there  is 
an  improvement,  which  consists  in  utilizing  a  smoked  brine. 
This  is  prepared  by  withdrawing  the  air  from  a  tank  contain- 
ing the  brine  and  forcing  the  smoke  into  it  under  pressure. 
Then  the  smoked  brine  is  applied  to  the  meat. 

Methods  are  used  on  a  considerable  commercial  scale  for 
preserving  meats  and  vegetables  by  withdrawing  the  air  from 
them  and  substituting  various  gases,  such  as  nitrogen  and  car- 
bonic acid  gas.  Argon  has  not  been  suggested  for  the  purpose 
as  yet,  but  before  long  it  will  be,  doubtless.  In  1853  Henry 
Hunt  took  out  the  first  patent  for  employing  the  vacuum  in 
canning  fruit  products,  such  as  would  suffer  injury  from  heat- 
ing. His  idea  was  to  exhaust  the  air  from  the  cans  in  order 
that  no  germs  of  putrefaction  might  remain.  A  singular  adap- 
tation of  the  same  notion  is  credited  to  N.  Raymer,  of  New 
Sterling,  N.  C,  who  invented  a  fruit- jar  stopper  with  a  short 
metal  tube  attached  to  it.      The  housewife,  when  she  has  closed 


AIR   PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  67 


Fig.  iS.— thk  vertical  twin  air  pump. 
Blake  pattern  for  marine  service.    Single  acting  beam.    G.  F.  Blake  Mfg.  Co.,  N.  Y.  City. 


68  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

a  filled  jar  of  fruit  with  such  a  stopper,  has  only  to  draw  a 
partial  vacuum  by  applying  a  small  pump  to  the  tube,  and 
pinch  it  with  pliers,  fusing  the  end  with  a  hot  iron  to  make  it 
air-tight. 

The  evaporation  of  fruits  and  vegetables  is  a  most  important 
industry,  and  owes  its  finest  output  to  the  vacuum  process. 

The  vast  sugar-refining  interests  of  the  world  are  dependent 
upon  the  vacuum  process  for  success  in  the  quality  of  this,  the 
sweetest  element  of  domestic  use. 

The  condensation  and  preservation  of  milk  has  become  a 
large  industry  in  Europe  and  the  United  »States,  and  its  per- 
fection is  greatly  due  to  the  vacuum  process  of  evaporation. 

One  of  the  most  useful  applications  of  the  vacuum  has  been 
for  the  preservation  of  wood.  vScores  of  patents  in  this  line 
have  been  granted.  So  far  back  as  the  year  1837  August 
Gotthilff,  of  New  York,  secured  exclusive  rights  in  a  process 
for  "  protecting  timber  from  destruction  by  worms,  dry  rot,  and 
other  causes  of  spontaneous  decay."  His  idea  was  to  exhaust 
the  air  from  the  wood  and  fill  up  the  pores  with  coal  tar  and 
turpentine.  In  this  direction  a  great  industry  has  since  grown 
up.  Piles  and  railway  timbers  are  impregnated  with  preserva- 
tive substances ;  while  metallic  solutions  are  employed  by  the 
vacuum  process  to  defend  our  wooden  ships  against  the 
depredations  of  the  devouring  shipworm  or  teredo. 

Wood  is  artificially  colored  by  using  the  vacuum  to  with- 
draw its  fluid  juices,  the  place  of  which  is  filled  with  solutions 
containing  pigments.  In  this  manner  ordinary  pine  may  be 
beautifully  stained  and  made  to  serve  as  a  substitute  for  rare 
and  costly  wood.  Lumber  is  seasoned  offhand  by  exhausting 
the  air  from  it,  and  then  forcing  dry  air  through  the  pores  to 
carry  off  the  moisture.  Wood  is  hardened  for  all  sorts  of  pur- 
poses, from  bridge-making  to  wagon-making,  by  a  vacuum  and 
pressure  process  called  "vulcanizing." 

The  variety  of  purposes  to  which  a  vacuum  may  be  applied 
seems  almost  endless,  and  aeain  we  contiTiue  the  enumeration 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  69 

of  lifting  of  acids  and  other  fluids,  exhaust  filters,  the  transfer 
of  sewage  from  cesspools  to  closed  tanks  on  wheels  for  removal, 
by  the  vacuum  process. 

The  operation  of  the  pneumatic  tube  system  for  cash,  tele- 
graph, and  postal  service  has  become  a  most  important  item  for 
the  rapid  transportation  of  mail  matter. 

A  system  of  transmitting  power  to  small  uses  by  a  vacuum 
pipe  system  was  tried  in  Paris,  France ;  but  was  discontinued 
or  changed  to  the  compressed-air  system.  The  great  forte 
in  the  usefulness  of  the  vacuum  has  been  found  in  the  low- 
pressure  system  of  steam  power,  which  owes  to  the  vacuum  the 
immense  development  in  the  steam  motive  power  of  the  present 
time.  Our  immense  steam  marine  owes  its  wonderful  economy 
of  one  pound  of  coal  per  hour  per  horse-power  to  compounding 
with  triple  and  quadruple  effect  derived  from  the  ultimate 
vacuum.  The  manufacture  of  ice  by  the  vacuum  process  has 
been  accomplished,  and  rooms  have  been  cooled  by  air  circula- 
tion around  chambers  of  ice  frozen  by  a  vacuum  process. 

DRVING  IN   VACUO. 

A  vast  saving  in  the  economic  values  of  many  by-products, 
consisting  of  wet  grains  from  breweries,  distilleries,  etc.,  and 
of  root  chips  from  beet-sugar  manufactories,  form,  in  many 
cases,  food-stuff  of  value ;  but  on  account  of  the  great  quantity 
of  water  they  contain,  they  are  subject  to  rapid  destruction  by 
decomposition,  and  their  nutritious  qualities,  especially,  suffer 
most.  The  same  cause  also  prohibits  their  carriage  over  any 
great  distance.  In  the  case  of  wet  beer  grains,  for  instance, 
carriage  has  to  be  paid  for  about  75  per  cent,  of  water.  Hith- 
erto, therefore,  it  has  been  necessary  to  utilize  these  by- 
products on  the  spot  where  they  are  produced,  or  at  least  in 
close  proximity  thereto,  as  well  as  with  the  least  possible  delay. 
The  natural  consequence  is  a  low  price  for  such  products,  of 
which,  moreover,  the  supply  is  often  greater  than  the  demand, 


■JO  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

and  thus  prevents  their  realizing  anything  like  their  market 
value,  particularly  during  the  hot  summer  months,  when  plenty 
of  other  food-stuff  is  to  be  had.  The  old  plan  of  preserving 
such  perishable  substances  in  pits  or  silos  is  only  a  very  rough 
and  poor  remedy  and  does  not  answer  its  purpose  at  all  com- 
pletely ;  for,  notwithstanding  all  precautions,  decomposition 
sets  in,  and  a  loss  of  as  much  as  50  per  cent  in  the  nutritious 
qualities  is  generally  sustained,  while  at  the  same  time  the 
moisture  is  by  no  means  reduced,  and  consequently  carriage 
still  remains  impracticable. 

It  has  long  been  endeavored  to  overcome  these  disadvan- 
tages by  removing  the  surplus  moisture  by  air-drying  the  by- 
products, so  as  to  allow  of  storing  and  transporting  them,  and 
at  the  same  time  realizing  their  full  market  value.  The  result 
of  such  endeavors  has  been  the  construction  of  different  kinds 
of  air-drying  machines,  which  has  certainly  been  a  step  in  the 
right  direction,  inasmuch  as  drying  is  undoubtedly  the  surest 
and  safest  way  of  preserving  perishable  substances.  The 
removal  of  the  water  overcomes  at  once  the  two  great  obstacles 
previously  encountered.  The  rapid  decomposition  ceases,  and 
carriage  to  a  distance  becomes  practicable,  and  the  reduction 
in  weight  is  very  considerable.  The  consequence  is  that  by- 
products, so  dried,  bring  their  full  market  value. 

The  process  of  air  drying  has  been  no  easy  task  on  account 
of  the  low  temperature  required,  wherever  it  is  wished  that 
the  dried  substance  should  retain  its  chemical  composition 
unchanged,  which  in  any  article  of  food  is  a  most  important 
point  for  enabling  a  profitable  result  to  be  obtained.  In  gen- 
eral two  drawbacks  have  rendered  themselves  conspicuous  in 
connection  with  the  air-drying  machines  hitherto  in  use; 
either,  in  order  to  shorten  the  drying  process  as  much  as 
possible,  and  to  make  it  sufficiently  economical,  too  great  a 
heat  has  been  employed,  with  the  unavoidable  result  of  seri- 
ously deteriorating  the  nutritious  qualities  of  the  material ;  or 
else,  when  a  longer  time  and  a  lower  temperature  have  been 


AIR   PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  J I 

employed  for  drying,  the  capacity  of  the  ordinary  drying 
machines  has  been  so  small  that  the  working  expenses  have 
rendered  the  process  unsuccessful  commercially. 

All  the  foregoing  disadvantages  are  avoided  if  the  boiling- 
point  of  water  is  lowered,  that  is,  if  the  evaporation  is  carried 
out  under  a  vacuum.  This  plan  is  widely  known  and  used  for 
liquids,  but  not  so  much  so  for  solid  substances.  For  the  latter 
it  has  first  been  successfully  applied  in  practice  by  the  vacuum- 
drying  apparatus,  which  is  designed  to  evaporate  large  quanti- 
ties of  water  contained  in  solid  substances,  in  as  short  a  time 
and  at  as  low  a  temperature  and  expense  as  possible. 

This  vacuum  plan  of  drying  is  already  in  use  for  various 
solid  substances,  and  the  result  has  in  every  case  been  remark- 
ably satisfactor}'.  Wet  grains  from  a  brewery  or  distillery, 
containing  from  75  to  78  per  cent  of  water,  have  by  this  drying 
process  been  converted  in  some  localities  from  a  worthless 
incumbrance  into  a  food-stuff  highly  valued  and  sought  after. 
The  water  is  removed  by  evaporation  only,  no  previous  mechan- 
ical pressing  being  resorted  to ;  hence  absolutely  the  whole  of 
the  solid  matter  is  retained,  of  which,  in  any  process  of  press- 
ing, a  large  proportion  would  have  been  carried  off  in  a  dis- 
solved state  in  the  water.  The  result  is  a  dry  food  stuff,  rich 
in  quality  and  satisfactory  in  appearance. 

From  malt  the  removal  of  the  moisture  which  it  contains 
has  to  be  effected  very  carefully,  and  required  in  the  old-fash- 
ioned kilns  as  much  as  forty-eight  hours,  because  the  low  tem- 
perature necessary  could  be  secured  only  by  slow  combustion ; 
this  method  was  and  always  is  a  risky  one.  In  the  first  stages 
of  the  drying  of  malt  the  temperature  has  to  be  kept  very  low; 
and  in  a  vacuum  apparatus,  therefore,  hot  water,  of  which  the 
temperature  is  easily  regulated  by  a  thermometer,  may  be 
used  instead  of  steam  as  the  heating  agent  at  the  outset,  while 
at  the  same  time  as  high  a  vacuum  as  possible  is  created  in  the 
drying  cylinders  by  an  air  pump  of  special  construction. 

If  all  the  water  were  evaporated  from  the  substances  to  be 


72  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

dried,  the  latter  would  of  course  be  heated  up  to  the  same  tem- 
perature as  the  heating  surface,  and  would  thereby  be  injured. 
This  was  one  of  the  drawbacks  connected  with  former  plans  of 
drying;  but  it  does  not  occur  in  the  regular  working  of  the 
vacuum  apparatus,  because  such  substances  as  beer  grains  or 
distillery  grains,  oats,  barley,  fruits,  and  vegetables,  are  never 
completely  dried,  but  are  always  taken  out  of  the  apparatus 
while  still  retaining  from  7  to  12  per  cent  of  moisture.  Even 
if  they  contained  less,  they  would  rapidly  absorb  again  from 
the  atmosphere  such  a  quantity  of  moisture  as  their  dry  con- 
dition in  the  atmosphere  allows. 

In  the  vacuum  process,  the  boiling-point  of  the  water  con- 
tained in  the  wet  material  is  brought  down  as  low  as  110°  F.  or 
43°  C. ;  the  difference  between  this  temperature  and  that  of  the 
heating  surfaces  is  amply  sufficient  for  obtaining  good  results 
from  the  employment  of  exhaust  steam  for  heating  all  the 
surfaces  of  the  vacuum  cylinder.  Under  atmospheric  pressure 
this  difference  of  temperature  would  not  exist ;  and  to  the  same 
cause  is  also  due  the  short  time  occupied  in  drying,  notwith- 
standing the  low  temperature  employed.  The  water  contained 
in  the  solid  substance  to  be  dried  evaporates  as  soon  as  the 
latter  is  heated  to  about  110°  F.,  and  as  long  as  there  is  any 
moisture  to  be  removed  the  solid  substance  is  not  heated  above 
this  temperature.  The  dried  product,  therefore,  remains  per- 
fectly unaltered  in  every  respect,  and  is  not  in  the  least 
impaired  in  its  chemical  composition  and  nutritious  properties 
by  the  drying  process. 

THE   VACUUM    IN    SALT-MAKING. 

The  manufacture  of  salt  by  the  vacuum  process  is  becom- 
ing an  important  item  in  the  industrial  economy  of  the  times, 
and  is  now  carried  on  in  Austria,  England,  and  the  United 
States.  We  illustrate.  Fig.  19,  the  initial  evaporating  section 
of  a  triple  effect  system  of  Dr.  S.  Pick,  of  Szczakowa,  Austria, 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE. 


7: 


which  is  in  section  of  the  first  effect  and  almost  self-explana- 
toiy.  The  three  pans  are  set  side  by  side,  as  in  a  triple  sugar 
apparatus,  and  the  terminal  connected  with  the  condenser  and 
air  pump. 

The  section  shows  the  boiling  chamber  A  (Fig.  19),  the  heat- 
ing chamber  B,  the  collecting  chamber  C,  and  the  filtering  cham- 
ber D.  The  three  sections  are  placed  side  by  side  a  few  feet 
apart,  and  are  connected  together  by  pipes  as  a  triple  effect. 
The  heating  chamber  /?  of  the  first 
section  is  placed  in  communication 
with  a  steam  boiler,  or  with  the  ex- 
haust steam  from  an  engine,  by 
means  of  the  pipe  E.  The  boiling 
chamber  A  of  the  first  section  is 
placed  in  communication  with  the 
heating  chamber  B  of  the  second 
section  by  means  of  the  pipe  F,  the 
second  boiling  chamber^'  communi- 
cating in  its  turn  with  the  heating 
chamber  i?^  of  the  third  section  by 
the  pipe  F\  This  latter  section  has 
its  boiling  chamber  placed  in  com- 
munication with  a  jet  condenser  and 
air  pump.  G  is  the  brine  inlet  pipe 
to  the  various  sections  and  is  in 
communication  with  the  brine  tanks, 

the  brine  being  raised  by  vacuum  and  supplied  automatically  to 
the  several  sections.  //  is  a  pipe  for  automatically  conducting 
the  brine  from  the  filtering  chambers,  D,  to  the  boiling  chamber 
of  each  section.  /  is  a  small  pipe  which  connects  the  boiling 
chamber  of  the  first  and  second  sections  with  the  condenser,  and 
is  used  for  assisting  in  maintaining  a  vacuum  in  each  of  those 
chambers.  In  like  manner  K  is  a  small  pipe  for  assisting  the 
vacuum  in  the  heating  chambers  of  the  second  and  third  sec- 
tions by  clearing  them  of  surplus  air  (not  shown  in  cut). 


steam  Trap 
Fig.  19.— vacuum  salt  pan. 


74  COMPRESSED    AIR   AND    ITS    APPLICATIONS, 

The  boiling  chamber  of  each  section  is  simply  an  iron  cylin- 
der, of  larger  diameter  than  the  heating  chamber  beneath  it. 
The  object  of  the  increased  diameter  is  to  enable  the  chamber 
to  contain  a  large  quantity  of  brine  with  a  minimum  of  depth 
and  a  maximum  of  evaporating  surface.  The  usual  level  of 
the  brine  is  seen  in  the  section,  which  is  a  sectional  view  of  a 
single  apparatus,  the  second  and  third  sections  not  being 
shown.  The  heating  chamber  consists  of  a  series  of  conical 
tubes  of  comparatively  small  diameter  surrounding  a  central 
tube  of  larger  diameter,  as  shown  in  the  section.  The  whole 
of  the  tubes  are  inserted  in  a  tube  plate  at  top  and  bottom,  and 
inclosed  in  a  cylindrical  chamber,  into  which  steam  is  admitted 
in  the  first  section  by  the  pipe  E,  and  after  imparting  its  heat 
to  the  brine  it  is  condensed,  and  passes  away  to  a  steam  trap  as 
shown.  In  the  .second  and  third  sections  the  condensed  water 
is  drawn  off  by  pumps. 

The  reason  for  having  the  tubes  conical  is  to  prevent  scal- 
ing, or,  should  scaling  take  place,  that  it  may  be  easily 
removed,  the  larger  diameter  of  the  tubes  being  at  the  bottom. 

The  settling  chamber,  immediately  beneath  the  heating 
chamber,  serves  for  collecting  the  salt  as  it  is  precipitated.  It 
settles  readily,  as  no  movement  takes  place  in  the  brine  at  that 
point.  It  is  in  direct  communication  with  the  upper  or  boiling 
chamber  through  the  tubes  of  the  heating  chamber.  This  col- 
lecting chamber  terminates  in  a  sluice  valve,  and  is  in  this  way 
connected  with  the  vacuum  filter  beneath  it,  which  forms  an 
important  and  essential  feature  of  this  system.  Each  filter  con- 
sists of  an  upper  fixed  portion  and  a  lower  hinged  portion,  the 
filtering  medium  being  attached  to  the  lower  portion  of  the 
filter  at  its  junction  with  the  upper  part.  The  upper  part  is 
fitted  with  an  air  inlet  cock  and  a  water  pipe,  ending  in  a  rose 
for  washing  the  salt  if  necessary.  The  lower  part  of  the  filter 
is  connected  with  the  boiling  chamber  by  a  tube,  the  lower 
portion  of  which,  as  far  up  as  the  valve,  is  flexible,  and  yields 
when  the  filter  is  opened,  as  will  be  seen  from  the  dotted  lines. 


AIR    PRESSURES   BELOW    ATMOSPHERIC   PRESSURE.  75 

The  method  of  operating  this  system  is  briefly  as  follows : 
Each  of  the  three  sections  having  been  charged  with  brine  to 
the  proper  level,  which  is  that  indicated  in  the  boiling  chamber 
A,  steam  is  admitted  to  the  heating  chamber  of  the  first  section, 
in  which  the  highest  temperature  is  maintained.  The  brine  in 
that  section  becomes  quickly  heated,  and  the  steam  given  off 
from  that  brine  enters  the  heating  chamber  of  the  second  section, 
heating  the  brine  in  that  section.  The  steam  given  off  from 
the  brine  in  the  first  section,  after  doing  its  work  in  the  heating 
chamber  of  the  second  section,  condenses  and  produces  a 
vacuum  in  the  boiling  chamber  of  the  first  section,  which 
vacuum  is  aided,  if  necessary,  by  opening  the  valve  on  the 
connection  with  the  vacuum  pump.  The  pressure  being 
reduced,  the  brine  in  the  first  chamber  enters  into  violent 
ebullition  at  a  comparatively  low  temperature.  The  same 
process  is  repeated  in  the  second  section,  the  steam  chamber  of 
the  third  section  acting  as  a  condenser,  and  producing  a  vacuum 
in  the  boiling  chamber  of  the  second  section.  The  steam  gen- 
erated in  the  third  section  is  drawn  off  by  the  vacuum  pump 
and  condensed  by  the  jet  condenser,  not  shown.  It  will  be 
seen  that  the  highest  vacuum  and  the  lowest  temperature  exist 
in  the  third  section,  while  the  highest  temperature  and  the 
lowest  vacuum  occur  in  the  first  section.  As  the  salt  is  pre- 
cipitated it  settles  in  the  collecting  chamber,  and  at  stated 
intervals  the  sluice  valve  is  opened  and  the  salt  and  brine  are 
admitted  into  the  filtering  chamber.  After  settling  there  for  a 
few  seconds,  the  sluice  valve  is  closed  and  the  air  cock  on  the 
filter  is  opened.  The  valve  on  the  ascension  pipe  H  is  then 
opened,  and  in  a  few  seconds  more  the  whole  of  the  brine  in 
which  the  salt  lies  as  in  a  bath  is  automatically  transferred  to 
the  vacuum  chamber,  leaving  the  charge  of  salt  resting  on  the 
filtering  medium  and  perfectly  free  from  brine.  The  valve  on 
the  ascension  pipe  is  then  closed,  the  filter  opened,  and  the 
charge  withdrawn.  The  filter  is  then  closed  ready  for  another 
charofe  of  salt. 


76  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

It  will  be  observed  that  during  the  operation  of  letting 
down  the  charge  of  salt  and  withdrawing  it  from  the  vacuum 
filter,  it  is  not  necessary  to  stop  working,  the  process  of  evapor- 
ation and  production  being  thus  rendered  simultaneous  and 
continuous,  and,  above  all,  automatic.  The  Miller  system  of 
salt-making  is  similar,  only  that  a  pipe  leg  is  extended  down 
from  the  cone  to  a  tank  seal  with  a  hydrostatic  height  equal  to  a 
vacuum,  and  thus  does  away  with  the  complication  of  the  Pick 
system  for  the  delivery  of  the  salt.  They  are  in  operation  in 
the  salt  works  in  Michigan. 

The  multiple  effect  system  of  evaporation  of  liquids  has  so 
improved  of  late  years  that  we  illustrate  in  Fig.  20  one  of  the 
leading  methods  of  evaporation  by  forcing  the  liquids  through 
a  tube  system  divided  in  small  streams  in  contact  with  large 
heating  areas,  by  which  the  liquid  is  not  long  subjected  to 
heat,  as  in  the  process  of  boiling  in  large  volumes. 

The  illustration  (Fig.  20)  shows  the  Yaryan  multiple  effect 
in  section,  plan,  and  elevation.  The  operation  is  as  follows: 
The  steam,  which  may  be  either  the  exhaust  from  the  engine 
or  live  steam  direct  from  the  boiler,  is  led  into  the  cylindrical 
chamber  surrounding  the  coils  in  the  first  effect.  The  liquid  to 
be  concentrated  is  fed  into  the  first  tube  of  the  return  bend 
coils  of  the  first  effect  in  a  small  but  continuous  stream,  and 
immediately  begins  to  boil  violently,  becoming  a  mass  of  spray, 
containing  as  it  rushes  along  the  heated  tube  a  constantly 
increasing  proportion  of  steam.  The  inlet  end  of  the  coil 
being  closed  to  the  atmosphere,  and  the  steam  being  continually 
formed,  the  contents  are  propelled  through  the  tubes  at  a  high 
velocity,  finally  escaping  from  the  last  tube  of  the  coil  into  the 
separator.  Here  the  steam  or  vapor  of  evaporation,  with  its 
entrained  liquid,  which  has  been  reduced  in  volume  by  the 
evaporation,  is  discharged  with  considerable  force  against  the 
bafifie  plates,  as  shown  in  the  figure  at  the  upper  left-hand 
corner,  which  separates  the  liquid  from  the  steam,  causing  the 
former  to  fall  to  the  bottom  and  permitting  the  latter  to  pass 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE. 


71 


yS  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

off  through  an  ingeniously  contrived  catch-all,  which  effectually 
removes  any  liquids  still  remaining  into  the  chamber  surround- 
ing the  tubes  in  the  second  effect,  where  its  heat  produces  the 
further  evaporation  of  the  liquid.  In  the  second  effect  the 
liquid  is  led  from  the  bottom  of  the  separator  of  the  first  effect 
into  the  coils,  and  the  same  operation  takes  place  as  in  the  first 
effect,  and  so  on  through  the  entire  system,  whether  triple, 
quadruple,  or  more  effects  are  used,  the  volume  of  the  liquid 
being  constant!}^  reduced  in  each  effect.  The  steam  from  the 
final  effect  goes  to  the  condenser  and  the  vacuum  pump,  a  high 
vacuum  being  thereby  maintained  in  the  separating  chamber 
and  consequently  in  the  coils ;  hence  the  boiling-point  of  the 
liquids  is  at  a  lower  temperature  than  that  of  the  surrounding 
steam,  and  by  the  condensation  of  the  steam  from  the  previous 
effect  upon  the  cooler  pipes  in  this  effect  a  vacuum  of  a  less 
degree  is  maintained  in  the  next  succeeding  effect.  This  rela- 
tive reduction  in  pressure,  and  consequently  boiling-temper- 
ature, automatically  adjusts  itself,  however  many  effects  are 
used,  thus  effecting  the  boiling  of  the  liquid  by  the  steam  pro- 
duced by  its  own  evaporation  in  the  previous  effect.  In  Fig. 
2  1  is  shown  a  general  view  of  this  system  of  evaporation,  with 
the  final  condenser  and  vacuum  pump  at  the  right-hand  side. 

One  of  the  advantages  claimed  for  the  system  of  evapora- 
tion of  a  liquid  in  the  form  of  a  spray  subjected  to  heat  under 
a  vacuum  is  that  it  receives  the  heat  quickly,  and  is  concen- 
trated in  the  time  of  its  passage  through  the  tubes,  and  then 
relieved  of  its  contact  with  the  high  temperature  of  the  first 
effect  and  removed  to  a  lower  temperature  with  a  higher 
vacuum,  and  so  on  through  the  whole  number  of  effects. 

The  spraying  is  produced  by  the  admission  of  the  liquid  at 
pressure  through  a  small  orifice  in  a  large  tube,  surrounded  by 
the  heating  steam,  evaporation  commencing  at  once,  and  the 
steam  of  the  evaporation,  being  unable  to  escape  except  by 
the  path  taken  by  the  liquid,  by  its  expansive  force  blows  the 
small  stream,  already  much  broken  up,  into  spray. 


AIR    PRESSURES    BELOW   ATMOSl'IIERIC    PRESSURE. 


79 


8o  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

The  rapid  motion  of  the  liquid  through  the  tubes  of  the 
Yaryan  system  has  the  further  advantages  that,  no  single  par- 
ticle remaining  long  in  contact  with  the  heated  surfaces,  in 
treatment  of  sugar  and  other  solutions  of  a  delicate  nature 
injury  from  overheating  is  avoided,  and  the  scouring  action  of 
the  combined  liquid  and  steam  greatly  reduces  the  liability  to 
form  scale. 

For  the  distillation  of  water  for  ice-making  and  for  steamers 
at  sea,  this  principle  seems  to  be  the  most  economical  conserver 
of  heat  known.  In  the  use  of  this  system,  with  coal  at  New 
York  prices,  pure  distilled  water  can  be  produced  at  a  cost  of 
fifty  cents  a  thousand  gallons,  or  less.  To  the  manufacturer  of 
ice  any  process  which  will  give  pure  distilled  water  free  from 
oil  by  use  of  the  exhaust  alone  of  the  compressor  is  a  desider- 
atum. vSuch  a  process  does  the  Yaryan  evaporator  afford.  The 
exhaust  steam,  instead  of  being  condensed  to  produce  the 
required  distilled  water,  is  used  only  to  evaporate  fresh  water 
for  distillation ;  hence  no  trace  of  oil  from  the  engine  can  be 
contained  in  the  distilled  water.  The  condensed  exhaust  is 
either  used  to  feed  the  boilers  or  goes  to  waste.  No  elaborate 
system  of  filtering  is  required,  and  hence  the  ice  is  always  clear 
and  transparent. 

The  address  of  the  Yaryan  Company  is  Tiuics  Building,  New 
York  City. 

In  Fig.  22  is  illustrated  a  detailed  section  of  the  Lillie  sys- 
tem of  evaporating  and  concentrating  liquids  and  syrups.  It  is 
constructed  for  triple  and  quadruple  effect  by  the  vSugar  Appar- 
atus Manufacturing  Company,  Philadelphia,  Pa.  It  consists  of 
a  stack  of  slightly  inclined  evaporating  tubes  open  into  the 
steam  chamber  at  the  right  and  expanded  in  a  thick  tube  plate, 
which  separates  the  steam  chamber  from  the  evaporating 
chamber.  The  other  ends  of  the  tubes  are  closed  save  a 
minute  air  vent  in  the  closed  end  of  each,  by  which  the  tube  is 
relieved  of  air.  The  liquid  or  cane-juice  is  circulated  and 
spread  over  the  tubes  of  the  entire  stack  by  a  distributing  tube 


AIR    PRESSURES    BELOW   ATMOSPHERIC    PRESSURE. 


8l 


over  each  vertical  row  of  evaporating  tubes,  over  which  the 
liquid  Hows  to  the  bottom,  entering  a  receptacle  or  well,  and 
into  the  suction  pipe  of  a  centrifugal  circulating  pump. 

The  water  of  condensation  in  the  evaporating  tubes  Hows 
back  and  drops  to  the  bottom  of  the  steam  chamber  into  a  trap, 


Fig.   22.— LILLIK   EV.AHOKATOR. 


and  is  carried  to  the  next  cooler  effect,  in  which  chamber  it 
gives  up  a  portion  of  its  heat  as  vapor  to  assist  in  the  evapora- 
tion of  that  effect. 

In  the  case  of  the  multiple  effect  apparatus,  the  discharge 
from  the  bottom  of  the  centrifugal  pump  is  fed  to  the  next 
effect,   with  the   exception  of  the  last  effect,  whose  discharge 


82 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


is  the  concentrated  liquor,  and  goes  to  the  final  receptacle. 
Whether  the  system  of  evaporation  consists  of  any  number  of 
effects  from  one  to  four,  the  train  of  operations  are  solely 
dependent  upon  the  condenser  and  vacuum  pump  at  the  end  of 
the  train  for  the  efficiency  of  the  system. 

In  Fig.  23  is  illustrated  a  complete  setting  of  the  Lillie 
triple  effect  sugar  train. 

In  Fig.  24  is  represented  the  elevation  of  a  sugar  pan  work- 
ing on  the  dry  system  of  evaporation,  in  which  the  water  enter- 


FlG.    23.  — THt.   LU.LIK   THII'LE   EtFtCT. 


ing  the  condenser  and  the  condensed  steam,  instead  of  passing 
through  the  air  pump,  passes  down  a  stand-pipe  or  siphon  by 
gravity  to  a  cistern  about  35  feet  below  the  condenser,  and 
which  is  thereby  sealed  against  atmospheric  pressure.  In  this 
system  the  air  pumps  are  only  required  to  keep  the  system 
relieved  of  air  and  a  little  moisture  or  uncondensed  vapor.  In 
this  type  of  evaporator  a  series  of  copper  coils,  as  shown,  five 
in  number,  enter  the  evaporating  pan  from  a  header,  shown  on 
the  outside,  and  circling  around  on  the  inside  of  the  pan  until 
sufficient  surface  is  obtained  for  the  work  of  evaporation,  and 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  83 

joining  to  another  header,  from  which  the  water  of  condensa- 
tion from  the  heating  steam  is  drawn  off.  In  a  multiple  effect 
Fig.  24  represents  the  last  pan,  and  Fig.  25  represents  a  quad- 


FlG.   24.— ELEVATION  OF  A  SUGAR   PAN. 

Joseph  Oat  &  Sons,  Philadelphia,  Pa. 


ruple  effect,  in  which  the  fifth  pan  shown  in  the  cut  is  the 
finishing  pan  or  last  receptacle  from  which  the  syrup  is  drawn 
off  to  crystallize.  Sometimes  a  surface  condenser  is  used,  in 
which  a  second  pump  draws  off  the  water  of  condensation. 


84 


COMrRKSSEl)    AIR    AND    ITS    AI'I'LICATK  )NS. 


FlO.   25.      QUADKUPI.E   EFFECT  EVAPORATING  AI'PAKATUS. 
Joseph  Oat  &  Sons,  Philadelphia,  Pa. 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  85 

THE    SIPHON    AND    ITS    \VORK< 

The  simple  siphon  for  drawino-  liquids  was  known  in  many 
forms  to  the  Egyptians  generations  before  the  Christian  Era, 
and  was  much  in  use  among  the  Romans,  to  whom  was  well 
known  the  part  that  a  vacuum  had  in  its  operation,  for  it  was 
then  used  for  conveying  a  water-supply  over  elevations.  The 
only  improvement  in  modern  times  has  been  to  supply  means 
■for  discharging  the  air  while  the  siphon  is  running.  In  Fig. 
26  A  is  the  siphon,  which  can  be  operated  over  heights  of  25 
and  possibly  30  feet  under  ver}^  favorable  conditions  as  to  its 


Fig.  26.— the  siphon. 


length.  //  and  G  are  cocks  to  be  closed  when  first  filling  the 
siphon ;  B  an  air  chamber,  C  a  water  seal  for  the  cock  below 
the  air  chamber,  I)  a  funnel  for  filling  and  also  for  sealing  the 
upper  cock  against  air  leakage. 

The  air  that  accumulates  in  the  chamber  B,  by  the  opera- 
tion of  the  siphon,  may  be  discharged  by  closing  cock  C,  open- 
ing cock  I),  and  filling  the  chamber  with  water.  Close  I)  and 
open  C,  when  any  air  below  C  will  rise  into  the  chamber,  and 
water  will  take  its  place  without  stopping  the  running  of  the 
siphon. 

A  PNEUMATIC  VACUUM  EXCAVATOR. 

During  the  construction  of  the  Tay  Bridge  considerable 
difficulty  was  experienced  in  sinking  the  cylinders  for  the  piers, 
several  expedients  having  been  successively  fried    and   aban- 


86  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

doned.  At  length  Air.  Reeves,  one  of  the  engineers  engaged 
on  that  great  work,  succeeded  in  devising  an  excavator  on  the 
pneumatic  vacuum  principle,  by  means  of  which  the  sand  was 
sucked  up  from  within  the  cylinders  and  discharged  into  hop- 
pers, the  cylinders  following  down  the  displacement  of  the 
sand.  One  of  these  excavators,  or  sand  pumps,  as  they  are 
also  called,  has  been  completed  by  A.  Wilson  &  Co.,  of  the 
Vauxhall  Iron  Works,  England,  and  has  been  inspected  at 
work  on  their  premises  by  a  number  of  engineers.  The 
excavator  has  been  made  for  the  New  South  Wales  govern- 
ment, and  will  be  sent  to  Sydney,  N.  S.  W.,  where  it  will  be 
used  in  sinking  cylinders  in  connection  with  the  improvements 
now  in  progress  in  the  harbor  there.  The  apparatus  consists 
of  a  pair  of  cast-iron  cylinders  4  feet  in  diameter,  carried  on  a 
staging  and  placed  in  connection  at  their  tops  with  an  air 
pump  driven  by  a  small  steam-engine.  The  connections  are 
so  arranged  that  the  air  can  be  exhausted  either  from  one 
cylinder  singly  or  both  at  the  same  time.  The  bottoms  of  the 
cylinders  are  connected  with  a  suction  tube  t,}4  inches  in 
diameter,  which  leads  down  to  the  sand.  Here  again  it  is  so 
arranged  that  the  cylinders  can  be  worked  either  singly  or  in 
combination  by  means  of  self-acting  valves.  The  soil  is  dis- 
charged from  each  cylinder  by  a  trap-door  placed  in  its  front. 
The  engine  and  air  pump  are  carried  on  the  same  framing,  and 
the  whole  forms  a  very  compact  arrangement.  In  operation, 
the  engine  being  started,  the  air  is  exhausted  from  one  cylin- 
der; the  sand  and  soil  rushing  up  into  the  vacuum  thus  created 
soon  fill  the  cylinder,  the  fact  being  indicated  by  a  tell-tale. 
The  connection  is  then  made  between  the  air  pump  and  the 
second  cylinder,  and  that  is  similarly  filled,  during  which  time 
the  contents  of  the  first  cylinder  are  discharged,  and  it  is  ready 
for  the  air  pump  by  the  time  the  second  cylinder  is  full,  and  so 
the  process  continues  alternately  until  the  desired  end  has  been 
attained.  The  excavator  worked  successfully;  a  vacuum  of  24 
inches  was  maintained  during  exhaustion,   and   the  cylinders 


AIR    PRESSURES    BELOW    ATMOSPHERIC    PRESSURE.  87 

were  rapidly  filled  with  sand  and  water  from  a  pit,  the  con- 
tents being  quickly  discharged.  Besides  the  Tay  Bridge,  this 
excavator  has  been  advantageously  used  at  the  Dundee  Espla- 
nade, where  a  considerable  quantity  of  land  was  reclaimed  by  its 
aid.  It  also  succeeded  in  pumping  the  sand  from  a  wreck  at 
Fraserburgh,  which  led  to  the  recovery  of  the  vessel.  In  fact, 
the  pneumatic  excavator  appears  to  have  a  wide  field  of  prac- 
tical application  before  it. 


FLOW    OF   AIR    INTO    A    VACUUM. 

The  theoretical  velocity  of  air  flowing  into  a  vacuum,  if 
wholly  unobstructed,  is  V2gh,  or  the  square  root  of  the  sum  of 
twice  gravity  multiplied  by  the  height  of  the  atmosphere  of 
uniform  density  due  to  the  height  of  the  barometer,  which  at 
29.921  and  60°  F.  is  27,816  feet  in  height  and  variable  with  the 
pressure  of  the  barometer  at  any  place.  Twice  gravity  in 
middle  latitudes  is  assigned  as  64.344,  but  64.32  is  usually  ap- 
plied to  these  computations.  Then  V64.32  X  27,816  =  1,337.7, 
the  velocity  of  the  flow  of  the  atmosphere  into  a  vacuum  in  feet  per 
second,  at  the  above  pressure  and  temperature.  This  velocity  is 
claimed  to  be  constant  at  all  pressures, so  that  if  a  receiver  be  filled 
with  compressed  air  at  any  great  pressure,  the  velocity  from  an 
orifice  into  a  vacuum  would  be  the  same  during  the  time  of  dis- 
charge of  the  receiver  from  first  to  last,  although  the  pressure 
would  be  decreasing  by  the  escape  of  the  compressed  air.  But 
the  quantity  of  free  air  issuing  per  second  would  not  be  the 
same  for  different  pressures  in  the  receiver;  it  will  vary  as  the 
density  at  any  moment,  multiplied  by  the  coefficient  of  the 
orifice.  This  uniformity  of  velocity  of  air  flowing  into  a  vacuum 
at  all  pressures  does  not  hold  when  the  discharge  is  made  into 
the    atmosphere.     The    height   of   the    atmosphere,    due    to    i 

97816 

pound  absolute  air  pressure,  is  — =  1,892.2    feet,  and   the 

14.7 

formula  for  the    flow   of   air  through   orifices    for  differential 


88  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

pressures  may  then  be  used.  's/2g,  h  X  c  becomes  V2g,  Ji  —  h^Xc 
=  velocity,  in  which  /i,=  1,892.2  for  each  absolute  pound  of  back 
pressure  in  a  partial  vacuum  chamber,  and  c  a  coefficient  for 
the  form  of  the  orifice.  For  example,  air  at  atmospheric 
pressure  flowing  into  a  chamber  or  tank  at  about  half  atmos- 
pheric pressure,  or,  say,  7  pounds  absolute  pressure,  we  have 
1,892.2  X  7  for  the  atmospheric  height,  and  V2^.  X  '\/i3,245.4  = 
8.02  X  1 15.7  =  927.9,  theoretical  velocity,  and  927.9  x  c  =  ."/  = 
649.5,  the  actual  velocity  in  feet  per  second,  .7  being  the  as- 
sumed coefficient  for  the  orifice. 


Chapter  V. 

THE  FLOW 
OF  AIR   UNDER  PRESSURE 
FROM   ORIFICES 
INTO  THE  ATMOSPHERE 


THE      FLOW     OF     AIR     UNDER      PRESSURE 
ORIFICES    INTO    THE    ATMOSPHERE. 


FROM 


In  the  theoretical  velocity  for  the  disctiarge  of  air  into  the 
atmosphere  under  very  low  pressures,  less  than  one-quarter  of 
a  pound  per  square  inch,  as  measured  by  the  pressure  of  water 
in  inches  of  height,  the  variation  due  to  difference  in  air 
density  has  been  found  so  small  that  it  has  not  been  considered 
in  the  formula  which  was  made  the  basis  for  computing  Table 
X.,  as  follows:  Theoretical  velocity  =  square  root  of  pressure  in 
inches  of  water  X  66.  i  ;  which,  multiplied  by  the  coefficient  C 
for  a  nozzle  or  a  thin  plate,  gives  the  tabulated  velocities.  This 
table  is  based  on  the  experiments  of  Daubuisson  and  computed 
for  uniform  density.  The  coefficients  being  for  a  nozzle  of  good 
form  .93,  and  for  an  orifice  in  a  thin  plate  .65. 

TABLE  X. — Velocity  of  Air  Under  Low  Pressure,  in  Inches  of  Water, 
WITH  Equivalent  Pressure  in  Pounds  per  Square  Foot.  Temperature, 
62'  F.  Barometer,  30  Inches.  Theoretical  and  with  Nozzle  and 
Thin-Plate  Orifice.  (Box.) 


Inches 

of 
water 

Pounds 

per 
square 

foot. 

Theo- 
retical 

velocity, 
feet  per 
second. 

Nozzle 
.93  c. 

Thin 
plate 
.65  c. 

Inches 

of 
water. 

Pounds 

per 
square 

foot. 

Theo- 
retical 
velocity, 
feet  per 
second. 

Nozzle 

•  93  e. 

Thin 
plate 

.6s  c. 

O.OI 

0.052 

6.61 

6.14 

4.29 

0.8 

4-15 

59.1 

54.9 

38.4 

02 

.104 

9-35 

8.69 

6.07 

•9 

4.67 

62.7 

58.3 

40.7 

04 

.208 

13.2 

12.3 

8.58 

I.O 

5.19 

66.1 

61.4 

42.9 

07 

•363 

17.4 

16.2 

ir.3 

1.5 

7-79 

80.9 

75.2 

52.5 

I 

.519 

20.9 

19.4 

13.6 

2.0 

10.38 

93.5 

86.9 

60.7 

2 

1.038 

29.5 

27.4 

19.2 

2-5 

12.98 

104.0 

96.7 

67.6 

.3 

1.558 

36.2 

33-6 

23.5 

3.0 

15.58 

114.0 

106.0 

74.1 

4 

2.077 

41.8 

38.8 

27.2 

3.5 

18.18 

124.0 

115. 0 

8g.6 

45 

2.337 

44-3 

41.2 

28.8 

4.0 

20.77 

132.0 

123.0 

85.8 

5 

2.597 

46.7 

43-4 

30.3 

4-5 

23-37 

140.0 

130.0 

91.0 

6 

3. 116 

51.2 

47.6 

33.3 

5.0 

25.97 

148.0 

138.0 

96.2 

7 

3.635 

55-3 

51.4 

35-9 

6.0 

31.16 

162.0 

151. 0 

105.3 

The   coefficient  for  different  forms  of  orifices  and  nozzles 
should  be  applied  to  the  theoretical  velocities  in  all  cases.     For 


92 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


a  sharp  edge  in  a  thin  plate  use  the  coefficient  in  the  table,  and 
with  a  plate  witli  rounded  orifice  on  the  inside  a  coefficient  of 
from  .70  to  .75  may  be  used  according  to  the  amount  of  curva- 
ture. With  a  clean  cylindrical  ajutage  in  length  three  times 
its  diameter  a  coefficient  of  from  .85  to  .90  may  be  used,  if  the 
inner  edge  is  slightly  rounded. 

Fig.  27  approximates  the  best  form  of  curve  for  short  nozzles. 

The  best  form  of  curved  taper  nozzle  will  give  a  coefficient 

of  .96,  and  a  nozzle  of  the  Venturi  form,  as  illustrated  in   Fig. 

8,  will  still  further  the  velocity  to  the 
theoretical  figure  or  more. 

The  velocity  of  air  under  the  higher 
pressures  discharging  into  the  atnios- 
phere  has  been  much  the  subject  of  ex- 
periment and  discussion,  and  some  of 
our  mathematical  authors  have  formu- 
lated complex  equations  that  are  not 
satisfactory  in  meeting  reasonable  results 
throughout  the  scale  of  pressures.  We 
have  adopted  the  theory  of  falling  bodies 
and  gravity  as  more  applicable  to  the 
true  conditions  of  the  flow  of  air  from 
orifices  under  pressure  and  into  the  atmosphere.  For  this  pur- 
pose we  use  the  height  of  an  atmosphere  of  uniform  densit)^ 
equal  to  the  weight  or  pressure  of  the  atmosphere  at  sea  level 
with  the  barometer  at  29.921  inches,  or  a  pressure  of  14.7 
pounds  per  square  inch. 

Then  the  absolute  pressure  of  a  free  atmosphere,  14.7 
pounds  per  square  inch,  divided  by  the  assumed  or  receiver 
pressure  in  absolute  atmospheres,  which,  multiplied  b}'  the 
height  of  the  uniform  atmosphere  (27,8 16)  and  the  product  sub- 
tracted from  the  height  (27,816),  gives  the  proportion  of  the 
height  to  which  the  pressure  is  due,  the  square  root  of  which, 
multiplied  by  the  square  root  of  twice  gravit3%  equals  the 
theoretical  velocity  in  feet  per  second. 


Fig.   ?7  —AIR  JET   NOZZLE. 


THE    FLOW    OF    AIR    UNDER    PRESSURE    FROM    ORIFICES.        93 

For  example,  for  a  pressure  of  one  atmosphere,  or  14.7  pounds 


in  receiver,  the  expression  may  be  \/2<'-  x  I    27,816  —  — '—   or, 

29.4 

reducing,    8.02   X  \^  ~— ,   and   for  two  atmospheres,  8.02  x 


i'  27,816 


J 


For  50  pounds  gauge:    Pressure  =  3.    4--^-^   atmos.  -4-  al)- 

14.7 

solute  atmosphere  =  —  _l  -^  =  and 

4       14-;       4-405 


y  27,816  —  =  V2  1,500  X   8.02  =   1. 175    feet; 

4-405 

or  b}'  the  decimal  method,  the  ratio  of   the  absolute  pressures 

may  be  used,  viz. :  For  50  pounds  pressure,   —ZlL  =  .2272   and 

64.7 


\/27,8i6  —  (27,816  X  .2272)  =  V2i,496.3  =  146.61  X  8.02  = 
1,175  feet  theoretical  velocity,  as  before.  The  theoretical 
velocity  must  be  multiplied  by  the  coefficient  of  the  orifice  for 
the  actual  velocity.  The  form  of  an  air  jet  nozzle  is  of  great 
importance  for  some  uses  to  which  the  air  jet  is  applied.  If  a 
sharp,  quick-flowing  jet  is  required,  as  used  for  cleansing  and 
dusting,  the  inside  should  be  smooth  and  curved  from  the  butt 
to  the  tip,  of  which  Fig.  27  represents  the  type  of  best  form. 

For  a  longer  nozzle  of  best  form,  the  curves  may  take  an 
elongated  shape  by  extending  their  length  with  the  same  pro- 
portional lateral  dimensions. 

By  the  experiments  of  Poncelet,  Wantzel,  and  others,  it  was 
found  that  for  pressures  above  the  atmospheric  pressure  to  y^-^ , 
tV'  "2"'  ^'5'  ^O'  ^^^  ^*^°  atmospheres,  the  coefficient  with  a  thin 
plate  orifice  became  .65,  .64,  .57,  .54,  .45,  .436,  and  .423 
respectively,  and  with  a  short  tube  .834,  .82,  .71,  .6/,  .53,  .51, 
and  .487  respectively. 

There-  is  a  singular  anomaly  in  the  coefficients  for  a  short 
pipe  that  does  not  correspond  with  the  tabulated  advance  of 
the  theoretical  velocities,  or  of  those  from  an  orifice  in  a  thin 


94 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


plate,  as  derived  from  the  experiments  of  Poncelet,  Wantzel, 
vSt.  Venant,  and  others,  which  show  a  maximum  velocity  from 
short  pipes  at  a  pressure  of  50  atmospheres. 

From  these  considerations  the  following  Table  XI.  of 
theoretical  velocities,  with  coefficients  and  actual  velocities  from 
the  orifices  of  thin  plates  and  short  pipes,  has  been  computed : 


TABLE  XI. — Velocity  of  CoMPRESSKn  Air,  Theoretical  and  ikom  Orifices 
IN  A  Thin  Plate  and  from  Short  Pipes  of  a  Length  of  Three  Times 
THEIR  Diameters.  The  Coefficients  of  Contraction  Decrease  with 
THE  Increase  in  Pressure  and  are  Derived  from  the  Experiments  of 
Poncelet  and  Otheks. 


Pressure 
in 

I 
Theo- 

Okiftcf. in  Thin 
Pi..vrE. 

Shok- 

PlIM  . 

Pressure, 

Pounds 

retical 

inches  of 

per  square 

velocity. 

Coefficient 

Actual 

Coefficient 

Actual 

pheres. 

mercury. 

inch. 

feet  per 

of 

yelocitv. 

of 

velocity. 

second. 

contrac- 

feet 

contrac- 

feet per 

tion. 

per  second. 

tion. 

second 

0.0 1 

0.3 

0.147 

94-4 

o.r,5 

6r.4 

,       0.834 

87.7 

.066 

2.1 

I. 

246. 

-f'43 

1 58. 

.825 

203. 

.  10 

3- 

1-47 

2g9. 

.()4 

191. 

.820 

245^ 

.  136 

4.08 

2. 

348. 

■(>3 

219. 

.815 

283. 

.204 

6.12 

3- 

472. 

.62 

293. 

•795 

375^ 

.272 

S.16 

4- 

493- 

.61 

301. 

•775 

382. 

.340 

10.20 

s. 

552. 

•59 

326. 

•755 

4'7. 

.40S 

12.24 

6. 

604. 

-SS 

350. 

•733 

443^ 

•  50 

15. 

7-35 

f)73. 

■57 

384. 

.710 

478. 

•544 

16.32 

8. 

(>'}1- 

•  567 

395^ 

.704 

491. 

.611 

18.34 

9- 

741- 

.563 

417^ 

.694 

--J4- 

.680 

20.4 

10. 

780. 

•5^' 

437^ 

.686 

:  35^ 

.809 

24.2S 

12. 

855. 

.  ^  ^ 

470. 

.678 

580. 

I. 

30- 

14-7 

946. 

•  54 

5U. 

.670 

634^ 

2. 

60. 

29.4 

1,094. 

•  5" 

547. 

.600 

6:6. 

5- 

i5'i- 

73-5 

1,219. 

•  45 

54S- 

.540 

6qS. 

10. 

300. 

147- 

1.275- 

•  436 

556. 

.520 

663. 

2(J. 

600. 

294. 

1.304. 

•  432 

563. 

.507 

6O1. 

40. 

1 ,  200. 

588. 

1,323- 

.42S 

500. 

•  498 

659. 

100. 

3,000. 

1,470. 

i,33i- 

•423 

563. 

•487 

648. 

200. 

6, 000. 

2.940. 

1,334- 

.41S 

558- 

.470 

635^ 

TABLE  XII.^Fi.ow  oi-  Air  thkough  an  Orifice,  in  Cubic  Feet  of  Free 
Air  I'Er  Minute.  Flowing  from  a  Round  Hole  in  Receiver  into  the 
Atmosphere.  (William  Cox.) 


Diameter 

of 

orifice. 

Gauge  Pkessurk. 

2  lbs. 

5  lbs. 

10  lbs. 

15  lbs. 

20  lbs. 

25  lbs. 

30  lbs. 

Inch. 

1-64 

.038 

•0597 

.0842 

•  103 

.119 

•133 

.1^6 

1-32 

•153 

.242 

•  342 

.418 

.48^ 

•54" 

.632 

I-16 

.647 

•  965 

1.36 

1.67 

i^93 

2.16 

2.!;2 

'A 

2.435 

3.86 

5-45 

6.65 

1-1 

8.6 

10. 

X 

9-74 

15.40 

21. S 

26. 70 

30.  S 

34^5 

40. 

THE    FLOW    OF   AIR    UNDER    PRESSURE    FROM    ORIFICES.        95 
TABLE   XII.    {Continued). 


Diameter 

of 
orifice. 

G.AUGE  Pressure. 

2  lbs. 

5  lbs. 

10  lbs. 

15  lbs. 

20  lbs. 

25  lbs. 

30  lbs. 

Inch. 

v% 

21.95 

34.60 

49- 

60. 

69. 

77- 

90. 

^2 

39- 

61.60 

87. 

107. 

123. 

138. 

161. 

yi 

61. 

96.  50 

136. 

167. 

193- 

216. 

252. 

H 

87.60 

133- 

196. 

240. 

277- 

310. 

362. 

% 

119-50 

189. 

267. 

326. 

37S. 

422. 

493- 

I 

156. 

247. 

350. 

427.    . 

494. 

550. 

645. 

i^ 

242. 

384. 

543- 

665. 

770. 

860. 

1 ,  0(X). 

i^ 

350. 

550.    , 

780. 

960. 

2 

625. 

985- 

Diameter 

of 
orifice. 

' 

Gauge 

Prkssure. 

35  I'^s. 

40  lbs. 

45  lbs. 

50  lbs 

60  lbs. 

70  lbs.  1 

So  lbs 

90  lbs. 

100  lbs. 

125  lbs. 

Inch. 

1-64 

■  173 

.19 

.208 

.225 

.26 

•29s 

•33 

.364 

.40 

.486 

'-32 

71 

•77 

■843 

.914 

1.05 

1.19 

1 

33 

I 

47 

.61 

I  97 

1-16 

2 

80 

307 

336 

3.64 

4.2 

4.76 

^ 

32 

5 

87 

6-45 

•   785 

% 

II 

2 

12.27 

13-4 

14.50 

16.8 

19.      1 

21 

2 

23 

SO 

25^8 

31.4 

"6 

44 

7 

49.09 

53-8 

58.2 

67. 

76.     1 

85 

94 

103. 

125- 

H 

100 

110.45 

121. 

130. 

151- 

»7i. 

191 

211 

231. 

282. 

% 

1 79 

196-35 

215. 

232. 

268. 

304. 

340 

376 

412. 

502. 

Vs 

280 

306.80 

336. 

364- 

420. 

476. 

532 

^87 

645. 

785. 

H 

400 

441.79 

482. 

522. 

604. 

685. 

76s 

843 

925- 

% 

550 

601.32 

6-8. 

710. 

622. 

93°. 

1,004 

I 

715. 

785.40 

860. 

93°- 

i 

Chapter  VI. 


THE  POWER   OF  THE 
WIND 


THE    POWER    OF    THE    WIND. 


Fig.  28.— the  box  kite. 


The  power  of  the  wind  to  lift  bodies  is  well  exemplified  in 
the  kite,  and  one  of  its  most  successful  types  is  the  box  or  Har- 
grave  form,  as  illustrated  in  Fig.  28.  The  dimensions  are 
given  in  the  cut,  the  rear  box  being  the  same  width  as  the  for- 
ward one.  The  fore-and-aft  sticks  c,  c  may  be  made  of  tough 
pine  or  white  wood  f  inch  square;  the 
cross-pieces  d,  <•/,  d,  d,  and  the  vertical 
pieces  should  be  of  the  same  width, 
but  quite  thin  ;  \  inch  for  the  sides  and 
-|  inch  for  the  cross-pieces.  The 
diagonal  braces  i\  t\  r,  e,  should  be  of 
fine,  strong  fishline.  twine,  or,  better, 
fine  steel  wire,  for  least  resistance  to 
the  wind ;  all  the  corners  should  be 
tightly  wound  with  fine  strong  twine  and  the  fore-and-aft  sec- 
tions covered  with  fi.ne  glazed  muslin  sewed  to  the  frame. 

The  bridle,  a,  b,  should  be  double  and  6  feet  long,  fastened 
to  the  fore-and-aft  stick,  at  or  near  the  rear  side  of  the  front 
section,  and  slightly  adjustable  for  balancing  the  kite  by  trial. 

The  bird  form  of  kite,  as  used  for  centuries  by  the  Chinese, 
failed  to  impress  its  self-sustaining  principles  upon  the  Western 
world  until  recent  years,  when  tailless  kites  came  into  use  and 
the  box  form  became  a  useful  aerial  carrier  of  meteorological 
recording  instruments.  In  the  cut  Fig.  28  is  figured  the 
dimensions  of  a  6-foot  box  kite,  the  lifting  power  of  which  for 
a  5 -degree  angle  with  the  horizontal  course  of  the  wind  is  about 
three-tenths  of  a  pound  per  square  foot  of  the  surface  of  the  top 
and  bottom  members,  in  a  3  5 -mile  wind  at  the  level  of  the  kite, 
or  for  the  24  square  feet  about  7  pounds.     The  pull  of  the  kite 


lOO 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


may  be  considerable  more   for  friction   and   the  resistance   of 
the  frame. 

The  first  form  of  adjustable  tailless  kite  was  the  keel  kite, 
which  is  simply  a  diamond-shaped  Eddy  or  Malay  kite  fitted 
with  a  fin  or  keel  extending  the  entire  length  of  the  central  stick. 
The  width  of  the  keel  is  about  one-third  of  the  greatest  width 


Fig.  20.— hakgkave  km  e. 


of  the  kite.  The  bridle  is  attached  in  the  same  manner  as  that 
of  the  Eddy  kite,  but  the  end  secured  to  the  tail  of  the  kite  is 
elastic,  so  that  in  a  strong  wind  it  stretches,  allowing  the  kite 
to  assume  a  smaller  angle  of  incidence  to  the  wind,  the  pressure 
of  which  upon  the  surface  of  the  kite  becomes  relatively  less. 
Kites  of  this  pattern  usually  fly  well,  but  are  very  liable  to  be- 
come distorted ;  and  when  driven  to  one  side  by  sudden  shifts  of 
wind,  they  recover  their  normal  position  less  rapidly  than  other 
kites.     The  Hargrave  kite  is  the  most  stable  of  those  in  use. 

The  addition  of  the  elastic  bridle,  previously  tried  on  the 
Eddy  and  keel  kites,  effected  a  marked  improvement.  Usually 
the  pull  exerted  upon  the  flying  line  by  a  rigid  Hargrave  kite 
without  an  elastic  bridle  is  extremely  variable  and  jerky,  hence 
destructive  alike  to  line  and  kite  frame  and  to  instruments 
carried  by  the  kite.  The  elastic  bridle  allows  the  kite  to  yield 
slightly  to  gusty  winds,  and  the  records  of  instruments  carried 
by  the  kites  are  as  steady  as  are  those  made  by  instruments 
resting  on  the  ground.  This  bridle  has  been  modified  and 
improved  from  time  to  time,  and  by  its  use  the  pull  upon  the 


THE    POWER    OF    THE    WIND.  lOI 

line  is  under  absolute  control.  The  elastic  may  be  adjusted  so 
that  the  pull  never  exceeds  a  certain  maximum  amount.  The 
action  of  the  bridle  is  shown  in  Fig.  29  and  the  method  of 
adjusting  in  the  two  positions.  The  elastic  portion  of  the 
bridle  is  shown  at  A,  while  B  represents  the  rigid  portion. 
In  light  winds  the  elastic  alone  receives  the  strain,  as  shown  in 
the  left-hand  diagram,  but  in  strong  winds  the  elastic  stretches 
until  part  of  the  strain  comes  on  the  rigid  cord  B,  which  is 
secured  to  the  front  of  the  kite.  The  angle  of  incidence  is 
then  very  much  less,  and  the  effective  pressure  of  the  wind 
relatively  diminished. 

In  Fig.  30  is  shown  an  adjustable  bridle  clip,  made  of  light 
metal,  Avith  small  rollers.  The  elastic  portion  of  the  bridle 
should  be  made  strong  enough  to  allow  the  kite  to  exert  a  pull 
of  one  pound  per  square  foot  of  lifting  surface,  or  say  24 
pounds  for  a  kite  of  the  dimensions  of  Fig.  28.  These  kites 
have  been  used  in  a  40  to  50  mile  wind  with  safety  when  prop- 
erly constructed  for  the  increased  pressure. 

]\Iuch  time  has  been  spent  in  efforts  to  improve  the  efficiency 
of  the  kites.  All  the  sticks,  wires,  etc.,  of  which  the  frames 
are  constructed  are  so  shaped  or  ar- 
ranged as  to  offer  the  least  possible  re- 
sistance to  the  air,  and  the  cloth  covers 
are  thinly  coated  with  paraffine  and 
ironed,  so  that  a  comparatively  smooth 
and   impervious  surface  is  obtained.      It 

^  Fig.  30.— bridle  clip. 

was  found   that   increasing  the  width  of 

the  rear  cell  of  the  kite  caused  it  to  fly  at  a  higher  angle ;  but 
since  the  pressure  of  the  wind  is  much  less  on  the  rear  than  on 
the  front  cell,  the  increased  weight  rendered  the  kite  less  effec- 
tive in  light  winds.  When  the  incidence  of  plane-surfaced 
kites  is  small,  as  it  is  when  the  elastic  bridle  is  employed  and  the 
kite  flown  in  high  winds,  the  wind  pressure  upon  the  edges  of 
the  kite  drive  it  backward  and  downward ;  and  while  such  kites 
fly  safely  in  and  are  not  injured  by  higher  velocities,  the  angular 


I02  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

altitude  reached  is  so  low  that  very  little  is  gained  in  attempts 
to  fly  them  in  wind  velocities  exceeding  40  miles  an  hour. 

Experiments  made  to  find  the  greatest  efficiency  of  the  box 
kite  has  shown  considerable  gain  by  curving  the  front  edges  of 
the  supporting  surfaces  upward,  as  shown  in  the  diagrams  in 
Fig.  29,     They  should  be  made  rigid  by  bent  wood  strips. 

Steel  piano  wire  is  used  for  the  larger-sized  kites  (No.  14), 
which  Aveighs  about  15  pounds  per  mile,  and  should  be  wound 
on  a  strong  hardwood  drum.  It  will  stand  a  working  pull  of 
100  pounds.  With  larger  size  kites,  say  of  50  square  feet  of 
lifting  surface,  meteorological  recording  instruments  have  been 
carried  to  a  height  of  12,000  feet. 

THE    WINDMILL   AND    ITS    WORK. 

The  velocity  and  force  of  the  wind  for  creating  power  was 
one  among  the  earliest  efforts  of  mankind  for  obtaining  work 
from  the  elements  of  nature. 

Without  going  into  details  of  the  tedious  progress  and 
development  of  wind  power  through  the  slow  march  of 
improvement  in  windmill  construction  during  the  many  cen- 
turies of  their  use  as  a  prime  mover,  the  final  outcome  for 
efficiency  seems  to  have  culminated  of  late  years  in  the  solid 
annular  slatted  form,  as  shown  in  Fig.  31,  or  the  segmental 
slatted  form,  which  reefs  to  the  wind  for  regulating  speed. 

The  American  type,  or  annular  sail  wind  motor,  which  pre- 
vails all  over  Canada  and  the  United  States,  is  now  being 
largely  introduced  into  Europe,  the  Oriental  and  South  Ameri- 
can countries.  In  this  type,  of  which  there  are  no  less  than 
twelve  varieties,  comprising  a  display  of  great  ingenuity  in  the 
scheming  of  their  gear,  the  sail  surface  is  an  annulus  or  broad 
ring,  formed  of  radial  slats.  Each  slat,  of  which  there  are, 
perhaps,  fifty,  is  a  small  sail  in  itself,  and  is,  in  most  cases,  set 
in  its  frame  at  a  fixed  angle  to  the  plane  of  motion,  the  effective 
wind  pressure  being  automatically  varied  by  making  the  wind 


THE    POWER    OF    THE    WIND. 


103 


wheel  slew  out  of,  or  away  from,  the  wind,  so  that  its  disk 
becomes  more  and  more  oblique  to  the  direction  of  the  wind  as 
the  pressure  increases,  thus  foreshortening  the  wheel  to  the 
wind.  This  form  has  a  single  vane  or  rudder  parallel  to  the 
axis,  and  carried  on  an  arm  springing  from  one  side  of  the  gear 
frame.  This  rudder  acts  against  the  resistance  of  a  weighted 
lever,  which  slews  the  wheel  back  into  the  wind  again  when 
the  pressure  subsides  to  the  normal.  This  variety  is  called  the 
"solid  wind  wheel,"  to  distinguish  it  from  those  forms  which 
have  sail- reefing  mechanism.  Of  the  latter,  one  form  in  par- 
ticular, which  seems  to  meet  with  most 
favor,  merits  description,  if  only  on 
account  of  its  curious  and  original 
reefing  mechanism. 

In  the  type  referred  to,  the  annulus 
is  made  up  of  six,  eight,  or  more  seg- 
mental frames,  each  carrying  a  num- 
ber of  fixed  vanes  and  pivoted  on  axes 
which  are  tangential  to  a  circle  de- 
scribed on  the  wheel  face.  This  wheel 
is  reefed,    both    automatically   and  by 

hand,  by  causing  the  sail  frames  to  turn  on  their  axes,  so  that, 
when  fully  reefed,  the  frames  assume  a  position  parallel  to  the 
main  axle,  and  are  then  quite  ineffective,  the  mill  being  there- 
by stopped.  Intermediate  positions,  of  course,  place  the  vane 
frames  more  or  less  obliquely  to  the  wind  by  means  of  a  large 
rudder  in  the  wake  of  it.  In  some  cases  the  reefing  gear  is 
actuated  by  a  centrifugal  governor.  This  mill,  when  seen  at 
rest  with  the  sails  fully  reefed,  presents  a  very  wreckish  and 
generally  startling  appearance.  It  is  strongly  suggestive  cf  a 
large  umbrella  which  has  had  its  ribs  unshipped  and  has  other- 
wise come  to  grief  in  a  gale  of  wind.  But  it  is  a  most  efficient 
conserver  of  wind  power. 

The  velocity  of  the  periphery  of  a  windmill,  constructed  as 
in  Fig.  31,  should  be  from  one  and  a  half  to  twice  the  velocity 


Fig. 


ihe:    modhkn    wind- 
mill. 


I04 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


of  the  wind  for  best  effect,  and  to  obtain  this  relation  the  angle 
of  the  slats  at  the  periphery  should  be  set  at  an  angle  of  i8° 
from  the  plane  of  the  wheel's  motion,  and  at  f  of  the  radius  of 
the  mill  the  angle  should  be  34°,  the  slats  having  a  gradual 
twist  to  meet  the  requirement  of  the  angles.  With  about  these 
angles  the  best  mills  are  now  built  in  sizes  from  S}6  to  30  feet 
in  diameter. 

The  actual  power  of  these  mills  as  taken  from  the  shaft  gear 
is:  Area  in  square  feet  of  the  slats  in  the  plane  of  revolution 
multiplied  by  the  cube  of  the  velocity  of  the  wind  in  feet  per 
second  equals  the  horse-power. 

The  average  velocity  of  the  wind  in  a  large  portion  of  the 
United  vStates,  and  for  the  lowest  force  that  will  do  effective 
work  with  a  windmill,  is  8  miles  per  hour  for  from  5,000  to 
6,000  hours  in  a  year,  and  an  average  of  16  miles  per  hour  may 
be  expected  for  3,000  hours  per  year;  so  that  for  a  power  that 
does  not  require  daily  attention  and  can  be  utilized  for  twenty- 
four  hours  of  the  day,  it  is  the  cheapest  for  all  uses  within  its 
sphere  of  action.  For  pumping  water  for  storage  for  all  uses, 
there  is  no  more  economical  prime  mover.  In  the  larger  sizes, 
of  50  and  60  feet  diameter,  wind  power  is  doing  excellent  work 
in  our  Western  States  for  milling,  and  in  all  sizes  is  largely 
extending  its  usefulness  in  irrigation.  The  following  table 
gives  the  sizes  of  windmills  in  common  use,  their  power  and 
capacity  for  pumping  water  with  an  average  of  a  16-mile  wind 
for  8  hours  per  day: 

TABLE   XIII.— The  Windmill  and  Its  Work. 


Diameter 
of  mill. 

Horse- 
power from 
shaft. 

Horse- 
power in 

water 
pumped. 

Gallons 

of  water 

15  feet  high 

per  hour. 

Irrigation 
in  acres, 
column  4. 

Gallons 

of  water 

25  feet  high 

per  hour. 

Irrigation 
in  acres, 
column  6. 

8«^  feet. 

0.09 

0.04 

616 

0.18 

370 

0. 10 

10 

.16 

.12 

1,918 

•  57 

1,151 

•339 

12         " 

■25 

.21 

3,420 

1.02 

2,036 

.60 

14 

.40 

.28 

4,530 

1-37 

2,708 

.798 

16 

■  50 

.41 

6,460 

1.84 

3.876 

1. 142 

18 

.70 

.61 

9.768 

2.83 

5.86r 

1.727 

20 

I. 

•79 

12.465 

3^65 

7.479 

2.20 

25 

1.50 

1-34 

21,233 

6.27 

12.743 

3^75 

30 

3- 

2.25 

3 1 , 660 

12.88 

19,000 

7.61 

THE    POWER   OF   THE    WIND. 


105 


THE    WINDMILL   FOR    ELECTRIC    LIGHTING. 

One  of  the  many  useful  applications  of  wind  power  is  exem- 
plified in  the  adaptation  of  the  windmill  as  a  prime  mover  for 
the  generation  of  electricity,  and  its  storage  for  lighting  and  for 
power  purposes  at  times 
when  the  wind  is  idle. 

In  Fig.  32  is  shown  the 
arrangement  for  gearing 
and  belting  a  windmill  to  a 
dynamo. 

The  windmill-driven  dy- 
namo charges  a  storage 
battery,  which  has  an  auto- 
matic cut-out  when  the  mill 
runs  too  fast  or  too  slow. 
The  mill  has  also  a  regula- 
tor throwing  it  out  of  the 
direct  course  of  the  wind 
when  running  too  fast,  or 
for  stopping  the  mill. 

A  windmill  30  feet  in 
diameter,  equal  to  3-horse- 
power  in  a  16-mile  wind, 
running  a  dynamo,  will 
generate  current  for  25  in- 
candescent lights  of  i6-candle  power  each.  To  run  a  plant 
of  this  kind  successfully  requires  some  means  of  obtaining 
current  when  there  is  no  wind,  or  when  the  wind  is  not  suffi- 
ciently strong  for  the  power  required.  Some  device  for  keeping 
the  electrical  pressure  at  the  required  figure  should  also  be 
employed.  For  supplying  current  when  the  wind  is  light,  or 
during  a  calm,  it  is  customary  to  use  a  storage-battery.  It  has 
also  been  proposed  to  run  a  pump  in  connection  with  the  wind- 


-FLKC  IKICriY  FROM   WIND  TOWER. 


I06  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

mill    and   to  store  water  in  a  tank,   or   convenient    reservoir, 
using  the  water  to  run  the  dynamo  by  means  of  a  turbine. 

To  steady  the  electrical  pressure  when  the  dynamo  is  run 
directly  from  the  windmill,  as  in  the  figure,  three  separate 
methods  can  be  employed.  A  specially  wound  dynamo,  giving 
a  constant  pressure  over  a  wide  range  of  armature  speeds,  is 
belted  directly  to  the  countershaft;  an  ordinary  dynamo  is 
driven  by  a  pair  of  cone  pulleys  placed  between  it  and  the 
countershaft,  a  governor  on  the  pulleys  regulating  the  speed 
ratio  between  the  countershaft  and  the  armature :  or  an  auto- 
matic regulator  is  arranged  to  place  storage-cells  in  circuit  with 
the  dynamo  as  the  speed  falls,  and  cut  them  out  as  the  speed 
rises. 

At  times  of  the  day  or  week  when  such  a  mill  is  not  used 
for  the  generation  of  electric  current  for  storage  or  direct  light- 
ing, it  will  also  supply  through  a  pump  the  water  required  for 
a  large  country  house.  For  the  purpose  of  irrigation  alone  the 
windmill  is  of  the  greatest  advantage  to  the  agricultural  inter- 
ests of  the  United  vStates,  and  even  in  our  Eastern  States,  where 
irrigation  has  been  heretofore  almost  totally  neglected,  it 
has  been  found  by  trials  that  by  the  use  of  a  windmill  with  a 
small  storage  capacity  for  water  to  ineet  contingencies  the 
increase  in  a  garden  or  small-fruit  crop  alone  will  amply  pay 
the  interest  on  th"e  plant,  and  in  seasons  of  severe  drought  the 
saving  will  pa}'  for  the  plant.  These  are  serious  matters  for 
consideration  and  for  the  success  of  our  gardeners  and  small- 
fruit  raisers.  Recently  a  windmill  has  been  erected  in  Ham- 
burg, Germany,  40  feet  in  diameter,  which  furnishes  120 
amperes  at  160  volts,  to  charge  accumulators  for  lighting  and 
the  operation  of  small  motors.  The  automatic  regulation  to 
meet  all  contingencies  of  the  wind  having  been  made  complete, 
this  system  of  generating  electric  power  seems  assured  of 
success. 


THE    POWER   OF   THE    WIND. 


107 


AIR   COMPRESSION    UNDER    LOW    PRESSURE. 


Fig.  33.— rotary  blower. 


Beyond  the  power  of  the  ordinary  bellows  and  centrifugal 
rotary  blower,  the  use  of  air  under  slightly  higher  pressure  is 
often  desirable,  and  for  this  purpose 
the  double  rotary  blower  is  a  most 
useful  device  for  obtaining  pres- 
sures up  to  3  pounds  per  square 
inch.  Fig.  33  is  the  form  of  the 
Root  blower,  in  which  the  extended 
surface  of  the  periphery  of  the 
wheels  allows    them  to   run  loosely 

in  the  shell  without  friction,   and  with  very  small  loss  by  air 
leakage. 

This  class  of  blowers,  unlike  the  ordinary  fan,  can  be  run 
at  any  desired  low  speed,  and  its  pressure  is  positive  for  any 
measured  volume  of  air  under  3  pounds  per  square  inch. 
Another  form  of  light-pressure  air  compressor  is  the  compound 
fan  blowers  of  the  Clarke  and  Hodges  type.  The  one  shown 
in  Fig.  34  is  a  double  blower  with  triple  effect.  The  air  is 
drawn  in  at  each  side  of  the  blower  and  thrown  out  at  increas- 
ing pressure  successively  by  the  fans  on  each  side,  and  returned 

successively  by  the  stationary  parti- 
tions, with  a  final  discharge  at  the 
central  annular  chamber.  With  these 
blowers  a  pressure  of  from  6  to  9 
pounds  per  square  inch  is  obtained. 

One  of  the  curious  properties  of  air 
issuing  from  a  bell-shaped  nozzle  of  an 
air  pipe,  as  illustrated  in  Fig.  35,  is  to 
hold  a  light  ball  close  to  the  bell,  allowing  no  more  area  between 
the  ball  and  the  bell  than  the  area  of  the  smallest  diameter  of  the 
nozzle.  The  same  effect  is  also  shown  with  a  light  fiat  disk 
laid    on   another  disk,   with   an   orifice    through    which    air   is 


Fig.  34.— triple  blower. 


io8 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


Fig.  35.  — air  nozzle. 


Fig. 


36.— G  A  S  O  L  I  N  E 
TORCH. 


blown.  ]\Iuch  theorizing  ha.s  been  given  to  this  phenomenal 
action  ;  but  we  believe  it  may  be  plainly  seen  that  the  expand- 
ing air  in  both  cases  produces  a  reflex  or  coun- 
ter movement  of  the  outside  air  that  neutral- 
izes the  pressure  beneath 
the  ball  and  plate. 

The  atomizing  power  of 

air  under  the  low  pressure 

of  a   fan   or  a   foot   bellows 

is  a  most    useful    appliance 

in   laundries,  and  there  are 

many  examples  of  the  use 

of  air  for    atomizing    fluids 

in  medical  and  surgical  use 

and  the  toilet.     The  spraying  of  colors  on  pottery  and  coloring 

dressing  material   on  textile  goods  is  a  matter  of  economy  in 

their  manufacture. 

Air  under  low  pressure,  as  derived  from  the  operation  of  a 
simple  hand  pump,  is  much  in  use  for  torch-lights,  and  by 
plumbers  for  melting  solder,  and  by  braziers. 

The  bicycle  and  vehicle  tire  pump  is  too  well  knowm  to 
need  special  description. 

The  air  and  gasoline  torch,  so  much  used  in  out-door  illu- 
mination in  street  and  construction  work,  is  shown  in  Fig.  36, 

and  consists  of  a  tank  into 
which  a  hand-pump  is  in- 
serted, drawing  air  from  the 
open  top  through  the  piston 
and  discharging  it  beneath 
the  gasoline,  producing  a 
saturated  air  and  vapor  gas, 
which  is  carried  to  the 
Bunsen  burner  through  the  vertical  pipe.  The  additional  air 
for  combustion  is  regulated  at  the  burner,  and  the  vapor  at  the 
valve  in  the  pipe  near  the  tank,     A  gauge  shows  the  pressure. 


Fig.  37.— GASOLINE   SOLDERING  COPPER. 


THE    POWER    OF   THE   WIND. 


109 


Fig. 


58. —  AIR      GAS 
BRAZIER. 


A  small  charge  of  gasoline,  say,  one  pint  to  one  gallon  tank, 
gives  best  effect,  and  is  safe  for  all  this  class  of  air-gas  appara- 
tus. A  similar  apparatus,  Fig.  2)7 ^  is  used  for 
heating  soldering  coppers  made  hollow  and 
with  a  side  vent  in  the  copper  tip  for  relieving 
the  flame.  The  pump  forms  the  handle  of  the 
apparatus,  so  that  the  copper  can  be  used  on 
the  torch  apparatus  for  special  work  in  the 
open  air.  It  is  much  in  use  for  making  elec- 
tric wire  connections. 

The  use  of  air  and  gasoline  vapor  for  braz- 
ing is  much  in  use  for  small  work,  and  is  one 
of  the   most    convenient    means    for    brazing 
bicycle  parts.       In    Fig.    38    is    illustrated    a 
double-flame  brazing  apparatus  with  external 
air  pump  and  gauge.     The  handles  at  the  back  of  the  burners 
regulate  the  flow  of  the  air-vapor  to  the   Bunsen  burners,  and 
a  fire-brick  or  graphite  slab  forms  a  back  on  which  the  flame 
impinges  and  is  intensified. 

In  the  four-flame  brazier  (Fig. 39  )  the  flames  impinge  on  each 

other,  enabling  the  work  to  be  brazed  subject  to  heat  on  all  sides. 

Any  desired  pressure  may  be  stored  in  the  tanks  within  a 

safe     factor     of 

strength    and    the 

capacity    of    the 

hand    pump;    but 

the  flame  pressure 

must  be  regulated 

by  the  valves   for 

best    effect.       In 

this    connection    a 

very    simple    and 

efficient   jet    com- 
pressor may  be  made  for  home  work  in  brazing,  glass-blowing, 
etc.,  with  a  small  apparatus,  as  shown  in   Fig.  40,  in  which  a 


■■<l^P. 


Fig 


39.  — FOUR-FLAME       BRA- 
ZIER. 


FIG.   40. 


no  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

jet  of  water  from  a  nozzle  falling  through  the  tube  6"  draws  in 
air  through  a  side  tube  and  forces  it  into  the  air  chamber, 
where  the  water  and  air  separate  under  pressure.  The  water 
is  siphoned  off  through  the  water  seal  at  a  height  due  to  the 
required  pressure  and  the  force  of  the  jet. 

AIR    PRESSURE    IN    GOLD-MINING. 

The  winnowing  of  gold-bearing  sands  for  separating  the 
sand  and  dirt  from  the  particles  of  gold  is  in  use,  and  many 
machines  of  various  forms  are  in  operation  in  the  dry-placer 
gold-mining  districts.  An  ordinary  bellows  furnishes  an  air 
blast,  which  separates  the  fine  sand  and  dust 
from  the  gold  on  the  riffle  screens  and  blows 
the  dust  away.  A  gold  winnowing  machine 
is  illustrated  in  Fig.  41. 

AIR    PRESSURE    FOR    GRAIN   AND  VENTILATION. 

The  winnowing  and  cleaning  of  grain  is 
not  new,  and  its  aeration  in  bins  and  store- 
FiG.  41.  —  DRv-PLACER     houscs  is  ouc  of  the  modern  economies  for 

MINING   MACHINE 

preserving  grain  from  must,  mildew,  and 
heating.  Air  under  the  higher  pressures  is  now  used  to  ven- 
tilate grain  bins  60  feet  in  height,  and  thus  obviate  the  neces- 
sity of  frequent  transfer  of  the  grain  for  its  aeration. 

The  motion  of  air  for  ventilation  is  so  well  known,  and  so 
ably  treated  in  works  on  ventilation  of  buildings  and  mines, 
that  we  refer  for  this  subject  to  such  works,  of  which  there  are 
many  published.  ^ 

COMPRESSED    AIR    FOR    BLOWING    GLASS. 

One  of  the  later  applications  of  compressed  air,  for  the  relief 
of  oppressed  humanity  in  regard  to  health  and  the  elimination 
of  disease  caused  by  the  artisan's  work,  is  in  the  blowing  of 
glass. 


THE    POWER   OF    THE    WIND.  Ill 

The  operation  of  blowing  is  hard  on  the  workman,  not  only 
because  of  the  muscular  effort  that  it  imposes  on  him,  but  also 
because  of  the  great  volume  of  air  that  he  has  to  draw  into  his 
lungs  within  a  very  short  space  of  time.  Such  defective  con- 
ditions are  further  aggravated  by  the  high  temperature  and  dry 
atmosphere  of  the  place  in  which  he  has  to  move,  and  this 
makes  him  liable  to  special  affections,  such  as  ulceration  of  the 
lips;  deglutination  and  distention  of  the  cheeks,  leading  to  the 
formation  of  nacreous  patches — an  indication  of  an  alteration  in 
the  mucous  membrane ;  fistulas  of  the  salivary  canal ;  and  a 
predisposition  to  emphysema  and  hernia. 

As  the  blowing  is  very  often  performed  by  young  children 
during  their  development,  the  results  are  still  more  disastrous. 

In  order  to  overcome  these  inconveniences,  a  series  of 
apparatus  has  been  invented  with  a  view  to  securing  a  substi- 
tute for  blowing  by  mouth. 

The  difficulty  in  applying  blowing  apparatus  to  the  glass- 
worker's  tube  resides  in  the  fact  that  the  workman  is  obliged 
to  rotate  the  latter  continuously  in  order  to  keep  the  piece  of 
glass  that  is  being  worked  in  an  axis  that  is  sensibly  the  same- 
as  that  of  the  tool  that  supports  it.  The  position  of  this  tube 
varies  according  to  the  kind  of  work  being  done ;  so,  in  order 
to  satisfy  such  different  conditions,  there  have  been  constructed 
three  types  of  apparatus  to  be  used:  (i)  According  as  the  work- 
man is  making  the  glass  by  revolving  it  according  to  a  hori- 
zontal axis;  (2)  revolving  it  according  to  a  vertical  axis,  the 
glass  being  under  the  tube;  or  (3)  revolving  it  according  to  a 
vertical  axis,  the  glass  being  above  the  tube. 

This  apparatus,  moreover,  is  based  upon  the  use  of  an  air 
pipe,  into  which  the  workman  fits  his  tube,  and  of  an  auto- 
matically closing  cock  that  he  actuates  either  with  his  hand  or 
with  his  foot  through  the  intermedium  of  levers,  so  as  to  pro- 
duce the  expansion  that  he  requires. 

For  the  blowing  of  glass  that  is  to  be  rolled  a  leather  pipe 
is  applied  to  the  blowing  tube  by  the  boy  who  helps  the  work- 


112  comi'ress?:d  air  and  its  applications. 

man ;  such  is  the  case  in  the  manufacture  of  tubes  and  of 
cylinders  for  window  glass.  In  this  case  the  compressed  air  is 
distributed  on  an  inclined  plane,  over  which  descend  the  dis- 
tributing pipes. 

The  advantages  derived  from  the  use  of  compressed  air 
are  of  several  kinds :  It  permits,  in  the  manufacture  of  drink- 
ing glasses,  to  do  away  entirely  with  blowing  by  the  mouths 
of  children,  and,  with  very  rare  exceptions  (mostly  through 
inattention  of  the  workman),  with  blowing  by  the  mouths  of 
adults. 

It  protects  the  latter,  then,  against  the  special  affections  that 
were  brought  on  by  the  old  method  of  blowing.  There  being 
less  fatigue  for  the  workman,  he  produces  better  work  and  a 
greater  quantity  of  it,  and  the  articles  are  manufactured  with 
greater  precision.  Finally,  the  use  of  this  process  permits  of 
obtaining,  without  fatigue  to  the  men,  articles  of  dimensions 
that  have  been  hitherto  unknown,  both  as  regards  bulk  and 
other  dimensions,  such  as  length  and  thickness.  The  limits 
that  may  be  reached  are  governed  only  by  the  weight  of  the 
material  operated  upon.  This  process,  moreover,  is  very 
elastic,  since,  in  consequence  of  the  successive  expansions  that 
the  workman  produces  at  will,  the  pressure  may  ascend  from 
less  than  an  ounce  per  square  inch  to  several  pounds'  pressure. 
In  air-pressing  glass  in  moulds  it  is  a  great  relief  to  the  strain 
on  the  lungs,  and  makes  better  work,  due  to  greater  control  of 
the  pressure. 


Chapter  VII. 


ISOTHERMAL    COMPRESSION 

AND 

EXPANSION  OF  AIR 


ISOTHERMAL    COMPRESSION    AND    EXPANSION    OF 

AIR. 

The  free  air  of  the  atmosphere  in  its  natural  condition  may 
be  considered,  in  all  ordinary  computations  for  its  use  by  com- 
pression or  expansion,  as  a  perfect  gas,  although  there  are 
small  differences  of  effect  due  to  moisture,  which  modifies  the 
density  of  air  under  the  process  of  compression  and  expansion, 
and  at  a  certain  degree  of  compression  seems  to  squeeze  out,  as 
we  may  say,  the  excess  of  vapor  upon  cooling  to  normal  tem- 
perature in  the  form  of  water  of  condensation.  The  vapor  of 
water  in  air  that  can  be  held  under  the  various  degrees  of  com- 
pression and  expansion  acts  like  the  properties  of  air,  but  is  of 
itself  lighter  than  the  other  constituents,  and  contributes  to  the 
atmosphere  the  weight  or  gravity  in  proportion  to  its  amount 
of  saturation.  Like  air  itself,  and  each  of  its  constituents  of 
the  so-called  permanent  gases,  moisture  is  liquefied  by  pressure 
and  the  lowering  of  temperature. 

Dry  air  being  a  mixture  of  several  gases,  which  at  ordinary 
pressures  and  temperatures  are  so  far  from  their  liquefying 
point  that  they  are  called  permanent  gases,  may,  for  all  prac- 
tical purposes,  be  considered  as  a  perfect  gas,  and  be  said  to 
obey  the  same  laws.  Any  gas  near  its  liquefying  point  is  called 
a  vapor,  and  we  may  then  say  that  the  difference  between  vapor 
and  gas  is  one  of  condition  only  rather  than  of  composition. 

Without  entering  upon  the  subject  of  the  molecular  consti- 
tution of  air  and  its  component  gases,  which  has  been  thor- 
oughly treated  in  the  able  works  of  Carnot,  Clausius,  Maxwell, 
Tyndall,  and  others,  we  will  first  consider  the  primary  laiv  of 
gases,  which  relates  to  the  isothermal  compression  and  expansion 
of  air. 


ii6 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


This  law  of  the  compression  and  expansion  of  air  and  of 
other  gases  witJiont  change  of  temperature  was  first  formulated 
by  Boyle,  in  England,  in  1662,  and  was  further  established 
by  Mariotte,  in  France,  in  1674.  It  is  called  Boyle's  law,  and 
relates  to  the  isothermal  compression  and  expansion  of  air  and 
other  gases,  and  was  written :  "  When  the  temperature  is  kept 
co)istant,  the  volume  of  a  given  gas  varies  inversely  as  its  pressure 
or  elastie  force  ;  that  is  to  say,  the  product  of  pressure  and  volume  is 
constant." 

This  has  been  since  found  not  absolutely  true,  for  in 
Regnault's  experiments  in    1847,  with  a    better  apparatus,    it 


%  "^     %         %  %  Absolute  Zero 

Fig.  42.— isothermal  diagram. 


was  found  that  the  product  of  volume  and  pressure  at  atmos- 
pheric pressure  14.7  ( V„,  P„),  divided  by  the  product  of  volume 
and  pressure  at  a  higher  pressure  (V^,  Pj,  resulted  in  a  slightly 
increased  volume,  v/hich  was  due  to  the  difference  in  pressure 
at  constant  temperature.  This  amount  was  very  small,  and 
increasing  to  but  .0063  of  the  volume  at  13  atmospheres,  so 
that  for  all  ordinar}^  computations  Boyle  and  Mariotte's  law 
represents  the  practical  requirements  of  isothermal  compression 
and  expansion.  According  to  this  law,  the  product  of  the 
volume  (V)  and  pressure  (?)  of  air  or  a  gas  is  always  a  constant 
quantity  at  the  same  temperature — that  is  to  say,  if  you  reduce 


ISOTHERMAL    COMPRESSION   AND    EXPANSION    OF    AIR.        I17 

a  given  volume  of  air  to  half  its  bulk  by  external  pressure, 
without  change  of  temperature,  then  the  pressure  will  be 
doubled,  and  by  inverting  the  operation  and  expanding  a  given 
volume  to  twice  its  bulk,  by  external  work,  without  change  of 
temperature,  the  pressure  will  be  reduced  one-half. 

A  graphic  diagram  of  the  pressure  curve,  due  to  isothermal 
compression,  may  be  readily  obtained  from  the  algebraic  ex- 
pression of  Boyle's  law  of  the  product  of  the  pressure  and 
volume.     Then  P  V  =  Constant. 

Let  P  =  the  initial  pressure  of  one  atmosphere  =14.7 
pounds  per  square  inch,  and  P,,  P^,  P.,,  P,,  the  vertical  ordi- 
nates  of  the  diagram  (Fig.  42)  representing  the  fractional  parts 
of  compression,  or  the  position  of  a  piston  at  different  points  in 
its  traverse  of  the  cylinder,  which  =  i. 

Let  P  O  represent  a  vertical  space  equal  to  one  atmosphere 
(14.7),  and  each  of  the  five  spaces  above  equal  to  P  O,  and 
number  them  i,  2,  3,  4,  5.  6  atmospheres.  Then  the  areas 
contained  in  the  rectangles  P,  i— P,,  2  — P,,  3  — P,,  4  — P4.  5— P5, 
6,  will  be  equal  to  one  another,  and  a  curve  meeting  the  points 
of  intersection  of  the  vertical  and  horizontal  ordinates  is  that  of 
a  hyperbola,  one  of  the  properties  of  which  is,  that  the  area 
of  the  rectangle  contained  by  the  horizontal  and  vertical  ordi- 
nates from  their  points  of  intersection  are  the  same,  or  equal 
in  area. 

Then  for  any  value  of  the  volume  V  as  at  a  half-stroke  of 
the  piston,  the  pressure  P  is  represented  by  an  inversion  of  the 
fraction  of  the  stroke  f ,  and  for  two-thirds  of  a  stroke  the  in- 
version of  the  reciprocal  of  the  fraction,  or  f,  represents  the 
pressure  in  atmospheres  from  the  absolute  zero  of  pressure, 
which  for  gauge  pressure  requires  the  atmospheric  pressure 
(14.7)  to  be  deducted.  Hence,  the  inverted  reciprocal  of  any 
fraction  of  the  travel  of  the  piston  in  isothermal  compression 
indicates  the  absolute  pressure. 

Then  for  obtaining  the  proportional  part  of  the  stroke  of  a 
piston  from  the  terminal,  for  any  desired  gauge  pressure,  divide 


I  18  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

the   absolute   or  atmospheric  pressure   (14.7)    by  the  absolute 

p 

pressure,  plus  the   gauge  pressure, ^  =  D,  the  distance  of 

the  piston  from  the  terminal. 

For  example:  at  75  pounds  of  gauge  pressure,  isothermally, 

I  zl   7 

the  piston  would  be  at    '^^^ — -  =  .  i6;8  of  its  stroke  from  the 

14-7+75 

terminal,  and  this  amount  will  also  represent  the  volume  of 
delivery  in  parts  of  the  whole  stroke,  neglecting  the  clearance 
space. 

In  this  manner  the  values  in  column  5  in  Table  XVII.  were 
computed,  which  also  shows  the  relative  volumes  of  com- 
pressed air  to  free  air  for  any  pressure  from  i  to  3,000  pounds 
at  the  normal  temperature  of  60°  F. 

In  column  3  of  Table  XVII.  is  shown  the  volume  of  free  air 
to  one  volume  of  compressed  air  at  the  gauge  pressures  in 
column  I,  and  is  computed  by  dividing  100  by  column  7  in 
Table  XVI.,  or  by  dividing  i  by  column  5  in  Table  XVI.  In 
column  7,  Table  XVII.,  is  shown  the  mean  isothermal  pressure 
per  full  piston  stroke,  neglecting  the  clearance,  which  of  itself 
will  slightly  lessen  the  mean  pressure. 

i  +  H 
This   was  computed  by  the  formula  p  X  — 5 —  —  P  =  mean 

pressure,  in  which  p  —  absolute  pressure,  or  the  acquired  gauge 
pressure  +  normal  pressure  (14.7).  R  =  the  ratio  of  the 
absolute  pressure  divided  by  the  normal  pressure,  and  H  the 
hyperbolic  logarithm  of  the  ratio  R :  P  =  the  normal  pressure 

(H.7)- 

Then,  for  example,  the  mean  pressure  for  isothermal  com- 
pression to  100  pounds  gauge  pressure  will  be  1 14.7  x  — 

—  14.7  =  30.193.      Ratio  R  = — ^— ^  =  7.8027,  the  logarithm  of 

14.7 

which  will  be  found  in  a  table  of  hyperbolic  logarithms,  or  the 

common  logarithm  multiplied  by  2.302585. 


Chapter  VIII. 


THERMODYNAMICS 


THERMODYNAMICS. 

Heat  for  a  long  time  was  supposed  to  be  a  special  sub- 
stance more  or  less  contained  in  air,  the  gases,  and  other  sub- 
stances, which  could  be  taken  up  or  intensified  by  compression 
or  squeezed  out  of  a  body,  as  air  or  gas,  and  the  tempera- 
ture of  a  body  was  thought  to  depend  upon  the  amount  of  the 
heat  substance  present  in  it.  The  phenomenon  appeared  ra- 
tional, but  later  investigations  pointed  to  the  vibratory  molec- 
ular theory  as  being  the  correct  solution  of  the  mystery. 

The  fact  that  heat  did  not  increase  the  weight  of  bodies  was 
a  stumbling-block,  and  many  ingenious  theories  were  adduced 
to  get  over  the  objectionable  features  of  the  early  theories,  yet 
none  proved  satisfactory.  The  relation  of  heat  to  and  its  effect 
upon  the  properties  of  air  and  its  constituents  is  undoubtedly 
no  longer  a  generic  hypothesis,  and  whether  it  be  molecular 
vibration  or  some  other  form  of  energy,  it  is  a  fact  in  regard 
to  its  influence  and  power  for  changing  the  condition  and  con- 
stitution of  matter.  Then  heat  is  a  form  of  energy,  free  from 
ponderability  and  possessing  the  power  of  entrance  into  all 
substances,  and  by  its  action  it  produces  work  through  the 
expansion  of  the  substance  in  which  it  acts,  by  virtue  of  such 
expansion  and  the  pressure  and  motion  induced  thereby. 

The  accepted  law  in  regard  to  the  expansion  and  contraction 
of  air  and  other  gases  by  changes  in  temperature,  or  their 
condition  in  relation  to  the  absorption  and  elimination  of  heat, 
was  formulated  by  Gay  Lussac  in  France,  and  Charles  in 
England. 

It  is  called  Gay  Lnssac's  Lazv,  or  the  second  law  of  perfect 
gases,  it  being  understood  that  a  perfect  gas  is  a  condition  in 
which  the  increments  of  expansion  and  contraction  are  exactly 


122  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

equal  throughout  the  whole  range  of  operation  for  both  volume 
and  temperature.  This  is  not  strictly  true  with  any  of  the 
so-called  permanent  gases,  for  it  is  now  found  that  all  gases 
are  only  the  vapors  of  liquids,  having  a  vastly  lower  tempera- 
ture degree  of  liquefaction  and  refrigeration  than  water. 

With  air  the  law  is  so  nearly  true  that  for  all  engineering 
purposes  it  is  accepted  in  ordinary  computation. 

Without  delving  into  the  relation  of  heat  to  other  bodies 
than  air  and  its  constituents,  we  need  only  formulate  the  rela- 
tion of  heat  to  the  expansion  and  contraction  of  air  as  composed 
of  its  constituents,  nitrogen,  oxygen,  argon,  carbon  dioxid,  and 
their  contained  vapor  of  water. 

Heat  becomes  a  means  of  compression  with  air  when  its 
volume  is  kept  at  a  constant  measure;  and  heat  is  made  mani- 
fest by  increase  of  temperature  when  a  measured  volume  of  air 
is  reduced  by  external  pressure.  The  terms  of  both  conditions 
are  of  equal  value :  the  heat  of  compression  and  the  cold  of 
expansion  are  positive  and  negative  equivalents  from  any 
initial  temperature. 

The  pressure  of  air  or  any  of  its  component  gases  is  exerted 
in  direct  proportion  to  its  variation  in  density,  and  both 
pressure  and  density  vary  inversely  as  the  volume,  supposing 
the  temperature  to  be  kept  constant. 

At  constant  volume  the  density  varies  as  the  pressure  and 
also  varies  as  the  absolute  temperature. 

Heat  as  a  mechanical  quantity  has  a  measure,  which  is 
gauged  by  its  effect  in  raising  one  pound  of  water  at  its  maxi- 
mum density,  through  one  degree  of  temperature  by  the 
Fahrenheit  scale.  It  is  called  the  British  tJicrmal  unit  to  dis- 
tinguish it  from  the  French  caloric,  which  is  the  quantity  of 
heat  required  to  raise  i  kilogramme  of  water  at  its  maximum 
density,  through  one  degree  Centigrade. 

Heat  and  mechanical  energy  are  mutually  convertible,  and 
are  measured  in  foot-pounds  of  power  per  heat  unit,  and  this 
relation  is  termed  the  First  Law  of  TJicrmodynaniics.     The  exact 


THERMODYNAMICS.  123 

value  of  its  measurement  from  experiments  of  Dr.  Joule,  in 
England,  and  of  Professor  Rowland,  in  the  United  States,  va- 
ries slightly  at  various  temperatures,  and  as  measured  by  the  air 
or  mercurial  thermometer,  the  extremes  of  which  are  from  772 
to  784  foot-pounds  per  British  thermal  unit.  The  number  778 
is  probably  nearly  correct,  and  will  be  used  in  this  work.  This 
value  is  sanctioned  by  good  authority,  and,  although  not  Dr. 
Joule's  figures,  it  is  termed  Joule' s  equivalent  and  designated  as 
a  mathematical  factor  by  the  letter  J. 

SPECIFIC    HEAT    OF   AIR. 

The  specific  heat  of  air  at  constant  pressure  varies  very 
slightly  with  the  variation  of  the  air  temperature  ranges  in 
which  the  experimental  data  were  obtained.  The  assignment  of 
the  average  amount  of  heat  required  to  raise  one  pound  of  air 
through  one  degree  of  temperature  was  found  by  Regnault  to 
be  0.2375  of  a  thermal  unit,  within  the  range  of  temperatures 
in  practical  use,  from  32°  to  328°  F. 

This  is  accepted  as  the  specific  heat  of  air  at  eonstant  pressure 
(cp)  during  which  the  volume  was  enlarged  during  the  absorp- 
tion of  heat. 

The  specific  heat  of  air  at  eonstant  volume  has  not  been 
found  accurately  by  direct  experiment,  but  has  been  deduced 
from  the  work  produced  by  the  expansion  of  a  given  volume  by 
the  air  value  of  one  thermal  unit  (.2375)  at  constant  pressure. 
This  was  found  by  Joule  to  be  equal  to  .0686  of  a  thermal  unit, 
and  .2375  —  .0686=  .1689,  the  accepted  value  of  the  specific 
heat  of  air  at  eonstant  volume  (cv). 

Then  using  the  mechanical  equivalent  for  one  thermal  unit 
as  a  basis  (778),  the  mechanical  equivalent  for  air  will  be  in 
proportion  to  its  specific  heat;  then  778  X  -2375  =  184.77,  the 
mechanical  equivalent  of  one  pound  of  air  at  eonstant  pressure 
(Mcp)  and  778  X  .1689=  131. 6,  the  mechanical  equivalent  of 
one  pound  of  air  at  eo>istant  volume  (Mcv). 


124  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

The  weight  of  one  cubic  foot  of  dry  air  at  sea  level,  barom- 
eter 29.921    and  32°   F.,  is  0.080728  lb.,  and - =  12.387 

.080728 

cubic  feet  in  one  pound  of  air  at  32^  F. 

Then  the  total  pressure  of  the  air  at  sea  level  per  square  foot 
(PJ  21 16.2,  multiplied  by  the  volume  of  i  lb.  (vj  12.387  c.  ft.,  and 
divided  by  the  absolute  temperature  from  32°  F.,  492.66,  equals 
the  difference  in  the  specific  heats  of  air  in  foot-pounds  at  con- 


staiit prcssui'c  and  at  coistaiit  I'ohinic,  viz. , 


2  I  16.2  X  12. 


jo/ 


53-17. 


492.66 

Then,  as  above  stated,  the  mechanical  equivalent  of  one  thermal 
unit  per  pound  of  air  at  constant  pressure  (^Icp)  =  184.77  ft.  lbs. 

and  at  constant  volnvie  (Mcv)  = 131 .60       " 

Difference  Mcp  —  Mpv  =  (D)  =    53.17       " 
53.17  as  a  ratio  will  be  noted  and  used  in  some  of  the  formulas 
further  on. 

The  specific  heat  of  air  has  been  found  by  experiments  of 
Professor  Linde  not  only  to  increase  by  its  temperature  den- 
sity, but  also  to  increase  by  density  from  compression.  He 
has  computed  an  interesting  table  of  these  values,  which  we 
here  reproduce : 

TABLE    XIV.— Spfx-ific    Heat    of    Air    at    Various    Temperatures    and 

Pressures. 


Temperature, 

Pressure  in  Atmospheres  and  Pou.xds. 

Fahrenheit. 

10 

20 

40 

70 

100 

14.7  lbs. 

147  lbs. 

294  lbs. 

588  lbs. 

1029  lbs. 

1470  lbs. 

212 

.2372 

.2389 

.2408 

.2446 

.2512 

.2583 

32 

•2375 

.2419 

.2465 

.2512 

•2773 

.2986 

-58 

.23S0 

•2455 

•2572 

•2785 

•3319 

.4124 

-  148    1 

.2389 

•2585 

.2844 

•3697 

•3461 

—  238 

•2424 

•3105 

.5048 

-274 

.2467 

•4147 

It  is  observed  by  inspection  of  the  table  that  the  specific 
heat  of  air  at  constant  temperature  increases  with  the  pressure, 
at  an  increasing  ratio  at  ordinary  temperatures,  and  is  over  25 
per  cent  at  32°  from  i  to  100  atmospheres,  the  specific  heat  at 


THERMODYNAMICS.  125 

32°,  .2375,  being  the  term  in  use  for  air  computations.  It  also 
increases  largely  with  its  density  from  increase  of  pressure  with 
decrease  of  temperature,  as  well  as  with  decrease  of  tempera- 
ture at  constant  pressure. 

ABSOLUTE   TEMPERATURE    AND    ITS    ZERO. 

The  recent  experiments  of  scientists,  and  especially  those 
who  have  been  operating  in  the  liquefaction  of  air  and  other 
gases,  seem  to  have  thrown  some  doubt  upon  what  has  hereto- 
fore been  conceded  as  absolute  ccro,  and  the  fact  of  an  absolute 
zero  has  been  lately  ridiculed  and  stated  to  be  a  "  thermody- 
namic heresy,"  and  that  the  beautiful  diagrams  drawn  from  its 
equations  or  formulas  are  misleading. 

We  take  no  stock  in  flimsy  denials  based  on  no  better  foun- 
dation than  mental  doubt.  The  operations  of  computation 
from  the  adopted  facts  and  formulas  work  well  within  the 
scope  of  practical  engineering,  and  it  is  safe  to  follow  them 
until  something  better  is  found  that  is  based  upon  an  equally 
good  foundation. 

So  that  it  may  be  taken  for  granted  that  the  zero  of  the  scale 
of  temperature  by  which  the  various  computations  in  Aerody- 
namics are  made  is  the  lower  terminal  in  the  heat  scale  at  which 
no  further  division  can  be  made  and  no  further  expansion  of 
air  or  gas  can  be  obtained.  It  is  the  equivalent  of  absolute  cold 
and  of  absolute  vacuum. 

The  lowest  temperature  that  has  as  yet  been  reached  experi- 
mentally is  that  of  frozen  liquid  air  at  a  temperature  of  —  404° 
F.  or  only  56°  above  the  computed  absolute  zero. 

In  order  to  obtain  the  starting-point  of  the  absolute  scale,  a 
backward  process  was  made,  based  upon  the  expansion  of  air 
through  a  measured  range  of  temperature  between  two  fixed 
points  that  are  well  known  and  reliable  in  thermometric  work. 

Regnault  found  that  if  a  volume  of  air  be  kept  constant  at 
various  initial  pressures  of  from  2.12  pounds  absolute  to  70.7 


126 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


K    Vol.  =  I  3ms 


pounds  absolute,  the  volume  when  heated  from  32  F.  to  212° 
F.  expanded  at  the  lowest  initial  pressure  to  1.36482  and  at 
the  highest  pressure  to  i. 37091,  a  difference  of  .00609,  which 
was  attributed  as  due  to  some  peculiar  property  of  an  imperfect 
,  gas  in  its  variable  expansion  under  different 
pressures.  It  may  have  been  from  the  in- 
fluence of  moisture  or  the  vapor  of  water  so 
difficult  to  eliminate  from  air  experiments, 
and  here  comes  the  basis  of  the  so-called 
"thermodynamic  heresies." 

At  atmospheric  pressure,  however,  the 
expansion  from  one  volume  was  found  to  be 
1.3665  intermediate  between  the  other  deter- 
minations, and  this  rate  was  adopted  for  ob- 
taining the  ratio  of  expansion  and  contraction 
per  degree  from  the  freezing-point  of  water 
(32°  F.)  and  its  boiling-point  (212°  F.). 
These  three  ratios  seem  to  indicate  a  curve 
in  the  expansion  line  above  and  the  contrac- 
tion line  below  the  trial  temperatures,  which 
might  extend  the  absolute  zero  far  below  the 
limit  as  com.puted  from  the  mean  ratio;  but 
as  this  has  not  been  fully  .shown  experi- 
mentally, the  adopted  ratio  seems  to  answer 
all  practical  purposes  within  the  ordinary  limits  of  engineering 
work. 

By  dividing  the  ratio  of  expansion  by  the  number  of  degrees 
over  which  it  extended,  the  ratio  for  each  degree  was  obtained, 

viz.,    'A — ^  =  .00203611  =  the  expansion  of  air  by  volume  for 
180°  •"  ^  ^ 


-tijt  4J3./3  Ab.  Zero 

■  —ico-ee 

Fig.  43. -scale  of  ab 
solute  zero. 


1°    rise    in    temperature;   therefore 


=  491.13,   which 


.0020361 1 

represents  the  number  of  degrees  equivalent  to  the  volume  (i) 
from  which  the  departure  for  expansion  from  absolute  zero  was 
started  ;  it  represents  the  number  of  degrees  below  the  freezing- 


THERMODYNAMICS.  12/ 

point  (2,2"  F.)  at  which  air  ceases  to  be  divisible  either  in  ex- 
pansion or  in  temperature;  and  491. 13  —  32°  =  459. 13  below 
zero  F.  was  adopted  for  the  absolute  zero  for  a  perfect  gas. 
This  value  has  been  much  used,  but  by  later  experiments  of 
Joule  and  Thompson,  and  probably  owing  to  a  small  variation 
in  the  relative  value  of  air  expansion  throughout  the  scale  of 
experiment,  the  absolute  zero  has  been  fixed  and  accepted  by 
good  authorities  at  492.66°  below  the  melting-point  of  ice 
(32°  F.)  and  at  460.66^  below  zero  F.,  and  will  be  so  used  in 
this  work. 

This  assignment  of  the  absolute  zero  (492.66)  makes  a  slight 
variation  of  the  ratios  used  for  the  computation  in  the  older 
tables  of  air  compression  and  expansion,  which  will  then  be- 
come  '- — =0.00202978  per  degree  Fahr.  for  extreme  tem- 

492.66 

peratures;  but  this  need  not  change  the  ratios  as  actually  found 
between  32^  and  212°  F.  (o. 0020361 1)  for  any  range  of  temper- 
ature in  ordinar}'  use ;  except  that  the  expansion  of  air  by  heat 
at  very  high  temperatures  may  not  follow  the  ratio  exactly. 

The  indications  are  that  there  appears  to  be  a  slight  curve 
in  the  expansion  line  from  32°  F.  to  the  absolute  zero,  which 
when  extended  from  212°  upward  may  slightly  increase  the 
volume  at  high  temperatures  as  computed  by  the  ratio. 

It  may  be  asked  whether  it  is  possible  that  air  or  gas  when 
deprived  of  all  sensible  heat  will  cease  to  occupy  space?  We 
answer  no!  For  at  this  time  it  is  well  known  that  all  gases  and 
their  compounds,  as  air,  are  but  vapors  of  liquids,  that  liquefy 
and  become  frozen  into  solids  before  the  temperature  of  abso- 
lute zero  is  reached.  Then  we  must  consider  that  the  absolute 
zero  of  our  ratio  scale  of  atmospheric  temperatures  is  the  point 
of  elimination  of  its  values  at  its  lowest  degree. 

With  the  ratio  of  .0020361 1  as  the  increase  per  unit  degree 
Fahr.  the  volume  and  pressure  may  be  computed  for  various 
temperatures  for  the  expansion  of  the  volume  of  one  pound  of 
air  expressed  in  cubic  feet,  and  also  for  the  pressure  of  a  con- 


128  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

stant  volume  by  change  of  temperature.  In  Table  XV.  are 
given  the  volume,  pressure,  and  density  of  air  at  various  press- 
ures from  o  to  3000°  F.  It  nearly  follows  the  ratio  given  above 
within  a  fraction. 

The  expressions  for  the  ratio  R,  for  the  inner  work  per- 
formed under  atmospheric  pressure,  may  be  written 

V  P        VP        VP 

T         t7  ~  t7* 

That  is,  if  we  divide  the  specific  volumes,  multiplied  by  their  cor- 
responding pressures,  by  the  corresponding  absolute  temperatures, 
the  quotients  are  constant  and  equal  to  R  or  53.17,  for  32"  F.  and 

for  the  pressure  per  square  inch  the  ratio  will  be  ^^'   '  =  0.3696. 

144 

rr.,  V„    X     Po  U  1       V„   X    P„  rp  1  R     X     T 

Then      "        -^'^  =  R,     and       °  _  ^"  =  T;     also    — — —    =    p., 
T  R  V„  ^" 

/I  R  X  T      ,. 

and  =  \"o. 

Po 

For  example,  one  pound  of  air  at  32°  F.  =  V„  or  12.387 
cubic  feet,  p„  =  atmospheric  pressure  14.7,  and  the  absolute 
temperature  at  32°  is  492  6. 


12.387  X  i4.7_    .^.A.o_Oo..-^  o.^  12.387  X  14. 


Then    ""  ^    zi^=  .369648  =  Ratio,  and 


492.6  .369648 

^        ,         .369648X492.6  „  -,    .369648x492.6 

492.6,     also       -^  ^     —     ^^ =  14.7,     and     -^  ^  ^ — ^_Jlz = 

12.387  14.7 

12.387,  following  the  equations  as  above  written. 

In  Table  XV.  the  ist  column  shows  the  degrees  of  tempera- 
ture from  0°  F.  to  3000°  F.  The  2d  column  shows  the  volume 
of  I  pound  of  air  at  the  different  temperatures  in  the  ist  col- 
umn. The  increase  in  volume  is  obtained  by  multiplying  the 
ratio  .0020361 1  by  the  number  of  degrees  above  32°  and  by  the 
volume  at  32°  (12.387),  and  to  the  product  add  the  volume 
12.387;  so  that,  for  example,  for  the  expansion  of  air  from  32° 
to  340°  we  have  a  difference  of  308°,  and  .00203611  X  308  X 
12.387  =  7.7681  +  12.387  =  20.155  cubic  feet  of  air,  equal  to  i 
pound  as  found  in  the  second  column  opposite  340°  in  the  ist 


THERMODYNAMICS. 


129 


column.     The  small  fractional  difference  arises  from  the  cutting 

off  of  fractions  in  the  terms  of  the  computation. 

V    X  t 
By  using  the  expression    -^^ for  the  volume  of  one  pound 

of  air  as  expanded  by  heat,  as  in  column  2,  Table  XV.,  the  vol- 
ume v„  =  12.387  at  32°,  and  at  360°  the  absolute  temperature  is 
360'^  -\-  460.6  =  820.6,  and  the  absolute  temperature  below  32°  is 

r         n^r,  -u      4.r-  ^-  12. 387  X   82O.6  ^  ,   . 

492.6.      i  hen,  as  by  the  equation,  — '^—^ =  20.63  cubic 

492.1 

feet  in  the  volume  at  360°  expanded  by  heat  from   32°  F.,  as 

given  in  column  2  opposite  360°  in  column  i. 

TABLE  XV. — Volume,   Pressure,  and  Density  of  Air  at  Various  Tempera- 
tures.    From  Normal  Volume  and  Pressure  at  62°  F.  (Haswell.) 


4)  lU 

4>6h 

Volume 

of  one  pound  of 

air  at 

atmospheric 

pressure, 
14.7  pounds. 

Absolute 

pressure  of  a 

constant 

volume  by 

heat. 

Weight  of 
one  cubic  foot 

of  free  air  at 
temperatures 

in  column  i. 

V    ■ 

Volume 

of  one  pound  of 

air  at 

atmospheric 

pressure, 
14.7  pounds. 

Absolute 

pressure  of  a 

constant 

volume  by 

heat. 

Weight  of 

one  cubic  foot 

of  free  air  at 

temperatures 

1     in  column  i. 

Cube  feet. 

Lbs.  per  sq.in 

Lbs. 

Cube  feet. 

Lbs.  per  sq.  in. 

Lbs. 

0° 

IX.583 

12. 96 

.086331 

360 

20.630 

23.080 

.048476 

32 

12.387 

13.86 

.080728 

380 

21. 131 

23.640 

.047323 

40 

12.586 

14-08 

•079439 

400 

21.634 

24. 200 

.046223 

50 

12.S40 

14-36 

.077884 

425 

22.262 

24.900 

.044920 

62 

13-141 

14.70 

.076097 

450 

22.890 

25.610 

.043686 

70 

13-342 

14.92 

.07.1950 

475 

23-51S 

26.310 

.042520 

80 

13-593 

15.21 

•073565 

500 

24.146 

27.010 

.041414 

90 

13-S45 

15-49 

.072230 

525 

24-775 

27.710 

.040364 

100 

14.096 

15-77 

.070942 

550 

25-403 

28.420 

•039365 

120 

14-592 

16.33 

.06S500 

575 

26.031 

29.120 

,038415 

140 

15.100 

16.89 

.066221 

600 

26.659 

29.820 

.037510 

160 

15.603 

17-50 

.064088 

650 

27-915 

31.230 

.035822 

180 

16.106 

18.02 

.062090 

700 

29.171 

32-635 

.034280 

200 

16.606 

18.58 

.060210 

750 

30.428 

34-040 

.032S65 

2tO 

16.860 

18.86 

■059313 

800 

31.681 

35-445 

.031561 

212 

16.910 

18.92 

•059135 

850 

32.941 

36.850 

.030358 

220 

17. Ill 

19.14 

.058442 

900 

34-197 

38.255 

.029242 

240 

17.612 

19.70 

•056774 

950 

35-454 

39.660 

.028206 

260 

18.116 

20.27 

.055200 

1,000 

36.811 

41-065 

.027241 

280 

18.621 

20  83 

.053710 

1,500 

49-375 

55.115 

.020295 

300 

19.121 

21.39 

.052297 

2,000 

61.940 

69.165 

.016172 

320 

19.624 

21-95 

•050959 

2,500 

74-565 

83.215 

.013441 

340 

20.126 

22.51 

.049686 

3,000 

87.130 

97-265 

.011499 

In   column  3   the  absolute   pressure  at  constant  volume  is 

•p  V  t 
obtained  from  the  equation  ^--— —  =  Pv,  and  for  the  pressure  at 

360  from  a  constant  volume  from  62°  F.  we  have  -^^ ^ 

522.6 

Q 


130  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

=  23.06,  and  so  on  for  any  desired  temperature  and  pressure 

from  the  values  of  absolute  pressure  and  temperature  p  and  t. 

The    4th    column    of    Table  XV.   is  the  weight  of   i   cubic 

foot  of  free  air  at  the  temperatures  in  column  i.     The  expres- 

D  X  T 
sion  =  D,,  in  which  D  is  the  density  of  air  or  the  weight 

of  I  cubic  foot  at  62°  F.,  T  the  absolute  temperature  from  62°, 
and  t  the  absolute  temperature  from  any  required  temperature. 

Then  for  the  density  at  360°  -Q/^OQ?    X    566.6   ^  .048476. 

820.6 

For  obtaining  the  volume  of  expansion  for  any  temperature 
not  found  in  the  table,  a  proportional  interpolation  of  quantities 
between  the  two  nearest  temperatures  in  the  table  will  be  found 
approximately  near  enough  for  all  practical  purposes. 

For  the  unit  value  of  pressure,  divide  the  greater  value  of 
expansion  by  the  lesser,  which  gives  the  ratio  due  to  the  lesser 
pressure ;  as,  for  example,  the  volume  of  one  pound  of  air  at  62° 

is  13. 141,  and  the  volume  at  340°  is  20. 126,  and  Z^-^ —    =  1.531, 

13. 141 

which  multiplied  by  the  atmospheric  pressure  for  the  lesser 
volume,  14.7  X  1.531  =  22.51,  the  absolute  pressure  of  a  con- 
stant volume  by  an  increase  in  temperature  from  62°  to  340°  F. 
Its  weight  per  cubic  foot  is  also  found  by  dividing  the  weight 
of  the  lesser  volume  in  column  4,  by  the  ratio  as  above,  1.531. 
For  the  cubic  feet  of  one  pound  of  air  at  any  temperature,  the 
weight  of  one  cubic  foot  of  air  at  60°  F.  multiplied  by  its  abso- 
lute temperature,  viz.,  .076097  X  522  —  39.7226,  a  constant  by 
which  the  cubic  feet  of  one  pound  of  air  at  any  other  temper- 
ature may  be  readily  computed.  For  example,  in  Table  XV. 
the  weight  of  one  cubic  foot  at  62°  F.  =  .0761  was  used,  which 
gives  the  constant  39.7242,     Then  the  value  of  one  pound  in 

cubic  feet  at  32°  is  — ^^^^ —  =  12.387,  and  for  100°  F.  is      ^ 


39.7242  39-7242 

=  14.097  cubic  feet  as  found  in  the  table. 

Another  useful  constant  is  derived  from  the  sum    of  the 
weight  of  one  cubic  foot  of  air  and  its  absolute  temperature. 


THERMODYNAMICS.  I3I 

divided  by  the  absolute  atmospheric  pressure  14.7.     Thus  say 

for  62°  F.    .0761  X  522°=  39.7242  as  before,   and     ^9-/-4-  _ 

14.7 

2.70204,  which  may  be  used  for  the  weight  of  one  cubic  foot  of 
air  at  any  pressure  and  temperature,  by  multiplying  the  con- 
stant by  the  absolute  pressure  and  dividing  the  product  by  the 
absolute  temperature.  Thus,  for  the  weight  of  one  cubic  foot 
of  air  at  sixty  pounds  pressure  and  62°  F.  temperature  we  have 

2.70204  X  74-7  o^^  A 

_^i_ "t  /^  /^  /  _   ^^355  pound. 


Chapter   IX. 


ADIABATIC  COMPRESSION 
AND  EXPANSION 


ADIABATIC   COMPRESSION    AND    EXPANSION. 

Having  shown  the  relation  of  compression  and  expansion 
of  air  as  a  perfect  gas  under  the  isothermic  law  of  Boyle  as  illus- 
trated in  Fig.  42,  the  action  of  heat  as  evolved  in  compression 
and  eliminated  in  expansion  of  air  becomes  a  most  important 
factor  in  the  practical  work  of  compression,  transmission,  and 
the  utilization  of  air  power. 

The  adiabatic  or  isotropic  lines  or  curves  representing  the 
moments  of  pressure  due  to  the  generation  of  heat  by  compres- 
sion or  the  elimination  of  heat  by  the  expansion  of  air,  may  be 
computed  and  expressed  in  diagrammatic  form  from  the  formulas 
representing  the  varying  conditions  of  increase  or  decrease  of 
progressive  pressure.  The  theoretical  curves  as  derived  from 
the  equations  represent  the  conditions  when  there  is  no  absorp- 
tion of  heat  by  the  walls  of  a  cylinder  in  which  the  operation  is 
taking  place.  In  practice  this  curve  is  never  produced,  but  a 
modified  form,  lying  between  the  theoretical  and  the  isothermal, 
is  the  resultant  as  produced  on  an  indicator  card. 

The  limiting  point  of  heat  by  the  compression  of  air  is  un- 
known, but  is  probably  at  the  pressure  of  liquefaction,  which 
has  not  yet  been  found  with  pressures  up  to  15,000  pounds  per 
square  inch  and  at  temperatures  raised  in  the  experimental 
compressors  and  receivers.  When  air  is  once  liquefied  by  press- 
ure and  artificial  cold,  it  has  been  found  to  hold  its  liquid  state 
at  about  12,000  pounds  pressure  per  square  inch  at  normal  tem- 
perature, 60"  F. 

Cooling  from  the  expansion  of  compressed  air  is  inversely  in 
the  same  ratio  as  from  compression ;  or,  the  temperature  falls 
by  the  same  scale  that  it  rises. 

As  we  have  said  above,  the  heat  saturation  point  is  probably 
at  the  pressure  of  liquefaction  ;  so  the  cold  extreme  from  expan- 


136  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

sion  is  probably  at  the  absolute  zero  of  expansion  or  perfect 
vacuum  ;  which  is  now  accepted  as  the  zero  of  absolute  temper- 
ature, 460.66°  below  the  zero  of  the  Fahrenheit  scale. 

The  difference  of  temperature  by  compression  for  equal  in- 
crements of  pressure  is  much  greater  in  the  lower  part  of  the 
compression  scale  than  in  the  upper  part;  as,  for  example,  the 
increase  of  temperature  from  atmospheric  pressure  to  one  pound 
per  square  inch  is  10°  F.,  while  for  an  increase  of  one  pound 
pressure  from  99  to  100  pounds  it  is  but  2.4°  F.  The  differences 
of  temperature  when  plotted  on  a  pressure  diagram  form  a  para- 
bolic curve  from  its  axis  at  absolute  zero  and  terminating  at 
infinite  pressure  and  temperature;  the  conditions  within  the 
limits  of  practice  indicate  this  curve,  as  also  its  inverse  order  in 
the  expansion  of  compressed  air. 

Compression  to  the  higher  figures  is  not  practicable  by  one 
stage  compression,  for  at  1,000  pounds  pressure  the  air  rises  to 
a  full  red  heat,  1313°  F.,  and  at  2,000  pounds  to  1709°  F. 

This  is  the  theoretical  temperature,  but  as  much  of  the  heat 
in  the  air  would  be  absorbed  by  the  compressor,  it  would  soon 
become  too  hot  for  economical  operation. 

The  three  elements  involved  in  expressing  the  adiabatic  con- 
dition of  air  or  a  gas  are  the  pressure,  volume,  and  absolute 
temperature.  The  quotient  is  always  the  same,  however  the 
pressure,  volum.e,  or  temperature  may  change;  given  any  two 
of  these,  the  other  may  be  readily  determined ;  for  the  absolute 
pressure  at  constant  volume  varies  with  the  absolute  temper- 
ature, (pv)  oc  T,  and  the  volume  at  constant  pressure  also  varies 
with  the  absolute  temperature,  (v)^,  a  T.  Then  in  the  work  of 
air  compression  pv>'  is  constant. 

Supposing  that  no  attempt  whatever  is  made  to  keep  the  air 
cool,  and  that  the  air  is  to  be  compressed  in  a  cylinder  which 
will  neither  take  up  any  of  the  heat  of  itself,  nor  allow  any  to 
pass  out  of  the  air  while  it  is  being  compressed ;  this  would  be 
a  case  of  adiabatic  compression,  and  we  should  find  that,  when 
the  volume  had  been  reduced  to  one-half,  the  pressure  would 


ADIABATIC    COMPRESSION    AND    EXPANSION. 


137 


not  be  double  only,  as  in  the  isothermal  case,  but  more  than 
double,  because  of  the  heat  generated  during  compression  being 
still  in  the  air;  or,  what  comes  to  the  same  thing,  when  any 
given  pressure  is  reached  there  would  be  a  greater  volume  of 
air,  owing  to  the  heat  in  it,  than  had  been  found  when  compres- 
sion up  to  that  same  pressure  had  been  isothermal.  In  making 
a  diagram  to  show  how  the  pressure  varies  in  such  a  case,  we 
must  take  into  account  not  only  the  reduction  of  volume,  but 
also  the  effect  of  the  heat  generated  while  that  reduction  is 
being  made.     The   molecular  theory  helps  us  to  understand 


At)aospherlc  Line 
Absolute  Zero  of  Pressure. 


Fig.   44.— ADIABATIC  COMPRESSION. 


why  heat  must  be  generated  during  both  kinds  of  compression, 
for  as  soon  as  the  piston  begins  to  move  it  increases  the  energy 
of  molecular  vibration  in  the  air  contained  by  the  cylinder,  and 
is  developed  into  activity  and  becomes  sensible. 

A  simple  way  of  making  a  diagram  of  adiabatic  compression 
is  to  draw  the  isothermal  curve  first  (the  dotted  line  in  the  fig- 
ure being  the  same  as  in  Fig.  42),  and  then  add  to  it,  at  various 
pressures,  the  extra  volume  due  to  the  heat  which  has  been 
generated  while  compressing  up  to  that  point.  This  extra  vol- 
ume can  be  found  by  taking  the  natural  number  which  corre- 
sponds to  two-sevenths  of  the  logarithm  of  the  absolute  pressure ; 


138  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

which  gives  the  ratio  of  volume  after  adiabatic  compression,  to 
volume  due  to  isothermal  compression.  Thus  at  2,  3,  and  4  at- 
mospheres absolute  the  volumes  would  be  1.22,  1.37,  and  1.48 
to  I  ;  and  as  the  power  expended  in  delivery  of  air  is  propor- 
tional to  the  final  volumes,  this  method  of  drawing  the  curve  is 
useful.  These  numbers  give  also  the  final  absolute  temperature 
in  terms  of  the  absolute  temperature  before  compression.  In 
the  equation  to  this  adiabatic  curve  r  =  1.406,  being  the  ratio 
of  the  specific  heats  at  constant  volume  and  constant  pressure. 
Then  following  the  diagram,  the 

Log.  of  2  is  0.30103,  which  multiplied  by  -i  =  0.0S6  which  is  log.  of  1.22 

"   3  "0.47712,       "  '•  "   1  =  0.136       "       "      "       "    1.37 

"       "   4  "  0.60206,       "  "  "   1  =  0.172       "       "     "       "    1.48 

and  so  on. 

Then  to  obtain  the  meeting  of  the  adiabatic  expansion  curve 
with  the  atmospheric  parallels,  the  differences  of  the  logarithms 

--> 
for  any  two  atmospheric    pressures  are  multiplied  by    —  and 

7 

their  logarithmic  indices  will  represent  the  volumes  from  the 
intersection  of  the  isothermic  curve  with  the  atmospheric  line; 
so  that  to  compute  for  the  points  in  the  curve  of  adiabatic 
expansion  in  Fig.  44  we  have  the 

log.  of  7  atmospheres  =  0.845098 

"      "    6  "  =0.778151 

1.045  index      0.066947 

and  -^ —  =  .95,  the  proportion  of  adiabatic  expansion  to  the 
1.045 

isothermal  expansion  on  the  line  of  6  atmospheres.  For  the 
terminal  of  expansion  in  volumes  of  free  air  in  proportion  to  the 
volumes  of  free  air  due  to  the  adiabatic  compression  to  7  abso- 
lute atmospheres,  then  cooled  to  normal  temperature,  the  log. 

-} 
of  7  =  0.845098  X  -    =  0.241456,  index  of  which  is  1.744,  ^nd 

7 

. — \ —  =  .573  per  cent  of  the  isothermal  volume  of  free  air,  as 
1.744 

shown  in  the  diagram  Fig.  44.     In  the  more  perfect  formula  for 


ADIABATIC    COMPRESSION   AND    EXPANSION. 


139 


the   heat  curve  of  adiabatic  compression  of  air,  the  terms  for 
each  increment  of  compression   are  equal  to  the  product  of  the 
volume  and  pressure  raised  to  the  heat  ratio  of    1.406,  and  the 
expression  for    each   in- 
crement of  pressure  will 
be  pv  '■"",  =  p,  V,  '■"",  = 

p„    v„  '■""    or  _        =  ^\ 
V.  p 

where  v  is  the  greater 
volume  and  p^  the  great- 
er pressure.  By  using 
Naperian  or  common 
logarithms,  the  expres 
sion    becomes    1.406    X 

log,        —  =  log.    i-i. 
V,  P 

The  thermal  result 
of  air  compression  and 
expansion  is  shown  by 
the  diagram  Fig.  45. 
Both  the  temperature  of 
the  air  and  its  volume 
are  shown  at  different 
stages  of  compression. 
The  simplest  application 
of  this  diagram  is  that 
which  gives  the  gauge 
pressure  represented    at 

different  points  of  the  stroke.  This  is  shown  in  the  horizontal 
lines.  But  in  compressing  air  we  produce  heat,  and  it  is  impor- 
tant to  know  the  temperature  at  any  given  pressure,  also  the 
relative  volume.  All  of  these  are  shown  in  the  diagram.  The 
initial  volume  of  air  equal  to  one  is  taken  and  divided  into  ten 
equal  parts,  each  division  between  two  vertical  lines,  shown  by  the 
figures  at  the  top,  representing  one-tenth  of  the  original  volume. 


21 

80 

to 

18 

17 

16 

15 

11 

2 13 

|12 
E 

a. 

■£) 

|io 

i  9 
8 

-oeS          do          cSdcSrfo 

291.0 
279.S 
2Ci.5 
249.9 

\ 

\ 

\ 

\ 

\ 

\ 

220.5 

\\       \ 

\ 

1 

19U 
176.1 
1C1.7 
147  0 

\!\ 

]\ 

\ 

1 

\ 

1 

1 

\a 

l\ 

% 

%\ 

"1 

U7.8 

'^\^ 

■o\ 

dl 

/ 

eX         \ 

1 

88.8 
73.3 
58.8 

11.1 

29,i 
tit 

C 
5 
1 
3 
2 
1 

■s. 

\\ 

\ 

7 

i 

\ 

\; 

C-f^ 

\X 

y 

.,^^\ 

K' 

\ 

k/* 

V 

s\ 

-^ 

^^r^ 

^ 

s\ 

0.0 

00       .t-         <o        "fl        ^        CO        e« 
Temperature  Fihrenheit 

Fig.  45.— adiabatic  diagram. 


I40  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

The  vertical  and  horizontal  lines  are  the  measures  of  vol- 
umes, pressures,  and  temperatures.  The  figures  at  the  left  in- 
dicate pressure  in  atmospheres  above  a  vacuum ;  the  corre- 
sponding figures  at  the  right  denote  pressures  by  the  gauge.  At 
the  top  are  volumes  from  one-tenth  to  one ;  at  the  bottom  de- 
grees of  temperature  from  zero  to  1,000''  F.  The  two  curves 
which  begin  at  the  lower  left-hand  corner  and  extend  to  the 
upper  right  are  the  lines  of  compression. 

These  curves  start  from  atmospheric  pressure,  and  in  all 
computations  for  pressure  the  zero  of  atmospheric  pressures  is 
the  starting-point,  which  would  be  represented  by  an  additional 
line  at  equal  distance  of  the  other  lines,  below  the  bottom  line. 

The  upper  curve  is  the  "adiabatic"  curve,  or  that  which 
represents  the  pressure  at  any  point  on  the  stroke,  with  the 
heat  developed  by  compression  remaining  in  the  air;  the  lower 
is  the  "  isothermal,"  or  the  pressure  curve  uninfluenced  by  heat. 
The  three  curves  which  begin  at  the  lower  right-hand  corner 
and  rise  to  the  left  are  heat  curves,  and  represent  the  increase 
of  temperature  corresponding  with  different  pressures  and  vol- 
umes, assuming  in  one  case  that  the  temperature  of  the  air  be- 
fore admission  to  the  compressor  is  zero,  in  another  60°,  and  in 
another  100°. 

Beginning  with  the  adiabatic  curve,  we  find  that  for  one 
volume  of  air,  when  compressed  without  cooling,  the  curve  in- 
tersects the  first  horizontal  line  at  a  point  between  0.6  and  0.7 
volume,  the  gauge  pressure  being  14.7  pounds.  If  we  assume 
that  this  air  was  admitted  to  the  compressor  at  a  temperature  of 
zero,  it  will  reach  about  100°  when  the  gauge  pressure  is  14.7 
pounds.  If  the  air  had  been  admitted  to  the  compressor  at  60°, 
it  would  register  about  176°  at  14.7  pounds  gauge  pressure. 
If  the  air  were  100°  before  compression,  it  would  go  up  to  about 
230°  at  this  pressure.  Following  this  adiabatic  curve  until  it 
intersects  line  No.  5,  representing  a  pressure  of  five  atmospheres 
above  a  vacuum  (58.8  pounds  gauge  pressure),  we  see  that  the 
total  increase  of  temperature  on  the  zero  heat  curve  is  about 


ADIABATIC    COMPRESSION   AND    EXPANSION.  I4I 

270°;  for  the  60°  curve  it  is  about  370"  ;  and  for  the  100'^  curve 
it  is  about  435°.  The  diagram  shows  that  when  a  volume  of  air 
is  compressed  adiabatically  to  2  i  atmospheres  (294  pounds  gauge 
pressure),  it  will  occupy  a  volume  a  little  more  than  one-tenth ; 
the  total  increase  of  temperature  with  an  initial  temperature  of 
zero,  is  about  650°;  with  60°  initial  temperature  it  is  800°,  and 
with  100°  initial  it  is  goo°.  It  will  be  observed  that  the  zero 
heat  curve  is  flatter  than  the  others,  indicating  that  when  free 
air  is  admitted  to  a  compressor  cold,  the  relative  increase  of  tem- 
perature is  less  than  when  the  air  is  hot.  This  points  to  the 
importance  of  low  initial  temperature.  It  is  plain  that  a  high 
initial  temperature  means  a  higher  temperature  throughout  the 
stroke  of  a  compressor.  The  diagram  gives  the  loss  of  temper- 
ature during  compression  from  initial  temperatures  of  0°,  60°, 
100°.  If  we  compare  the  compression  line  from  zero  with  the 
compression  line  from  100°,  we  observe  that  in  compressing  the 
air  from,  say,  i  atmosphere  to  10  atmospheres,  the  original  dif- 
ference, which  at  the  start  was  only  100°,  has  now  been  about 
doubled,  that  is,  it  has  reached  200°;  and  in  carrying  the  com- 
pression to  20  atmospheres,  the  difference  now  becomes  about 
250°.  Each  horizontal  division  represented  by  the  figures  at 
the  bottom  is  equal  to  100°,  and  the  space  between  any  two 
adjacent  horizontal  lines  may  be  subdivided  into  100  equal  parts 
representing  1°  each. 

Where  there  is  a  system  of  cooling  the  air  during  compres- 
sion, the  lines  on  the  indicator  cards  can  be  traced  between  the 
adiabatic  and  isothermal  curves  on  the  diagram.  In  practice, 
the  best  compressors  show  a  line  about  midway  between  these 
two  curves. 

For  all  practical  purposes  in  using  this  diagram,  it  is  best  to 
follow  the  adiabatic  curve  in  all  determinations,  except  where 
the  exact  pressure  line  is  known.  This  diagram  will  be  found 
convenient  to  those  who  are  called  upon  to  figure  the  pressure 
at  different  points  in  the  stroke  of  an  air  compressor,  and  it 
points  out  the  common  error  of  neglecting  to  take  into  consid- 


142  COMPRESSED   AIR   AND    ITS    APPLICATIONS. 

eration  in  one's  figures  the  fact  that,  at  the  beginning  of  the 
stroke,  one  atmosphere  in  volume  already  exists.  Beginning 
at  the  lower  left-hand  corner,  the  adiabatic  pressure  curve  in- 
tersects the  first  horizontal  line  at  that  point  in  the  stroke  where 
the  pressure  on  the  gauge  will  register  14.7  pounds. 

The  next  horizontal  line  shows  where  the  gauge  reaches 
29.4  pounds,  and  it  is  evident  here  that  the  piston  of  an  air 
compressor  travels  much  farther  in  reaching  14.7  pounds  than 
in  doubling  that  pressure  or  in  reaching  29.4  pounds;  thus  an 
air  compressor  is  an  engine  of  unevenly  distributed  resistance. 
During  the  early  stages  of  the  stroke  it  has  a  slowly  accumulating 
load  to  carry,  while  later  on  this  load  is  multiplied  very  rapidly. 

For  computing  the  pressure  at  the  intersection  of  the  adia- 
batic curve  with  the  horizontal  lines  in  the  diagram,  the  lines 
representing  the  volumes  of  compression  are  the  starting-points 

I      2 
in  the  formula,  and  the  com^pression    =^   ^,  ^,   etc.,   of  which 

10    10 

the  complements  ^,  — ,  etc.,  are  the  terms  of  the  volume  used 
10    10 

V  ''^ "        n  10 

in  the  equation.      Then  by  inversion,  —       =  £- and  —  =  i.iii 

V,  P  9 

log.  0.045714  X  1.406=  log.  0.064273,  of  which  the  index  is 
1. 159  in  absolute  atmospheres,  and  1.159—  i  =  .159  in  hun- 
dredths of  the  space  above  one  atmosphere  at  the  intersection 

of  the  first  vertical  line  representing  a  compression  of  —  and 

marked  .9  at  the  top  of  the  diagram.  For  the  position  of  the 
curve  at  the  second  vertical  line  and  following  the  same  nota- 
tion is  to  be  used,  viz.,  —  =1.25    log.   0.0961  X  1.406  =  log. 

o 

0.136255,  of  which  the  index  is  1.368  in  absolute  atmospheres 
and  1.368  —  I  =  .368  in  hundredths  of  the  space  at  the  inter- 
section of  the  second  vertical  line  representing  a  compression  of 

—  and  marked  .8  at  the  top  of  the  diagram.  At  the  compres- 
10 

sion  of  -^  and  marked  .  i  in  the  extension  of  the  diagram  the 
10 


ADIABATIC    COMPRESSION   AND    EXPANSION.  1 43 

point  of  intersection  with  the  adiabatic  curve  will  be  carried  up 
to  25.47  atmospheres. 

For  locating  the  isothermic  curve  the  first  index  of  the  com- 
pressions  is  to  be   used,   and    the    intersections    of    the   curve 

with  the  verticals  will  be  —  =   i .  1 1 1   absolute  atmospheres  and 

9 

1 .  1 1 1  —  I  =  .  1 1 1  on  the  scale  of  the  diagram  ,—-  =  1.25  —  1  = 

o 

.25,  and  so  on  for  each  intersection  on  the  isothermic  curve 
with  the  compression  verticals  of  the  diagram. 

For  the  temperature  curves  from  three  differenf  initial  tem- 
peratures of  0°,  60°,  and  100°,  the  temperature  of  compression 
for  each  increment  or  atmosphere  as  represented  in  the  diagram 
is  found  by  the  common  logarithm  of  the  quotient  of  the  abso- 
lute pressures  multiplied  by  the  exponent  of  the  ratio  of  ex- 

0.29  q- 

pansion  by  heat,  .2906.     Then -i-      =  __  x    100  to  correspond 

with  the  100°  divisions  at  the  bottom  of  the  diagram;  and  for 
the  gauge  pressure  of  14.7  pounds,  which  is  2  absolute  atmos- 
pheres   as    marked    on    the  left-hand  margin,    -^^   is    2,    log. 

14.7 

0.30103  X   .29  =  log.  0.0033298,  the  index  of  which  is    1.08  X 

100  =   108,  the  point  of  meeting  of  the  expansion  curve  with 

the  horizontal  line  representing  2  atmospheres  absolute. 

Then  for  the  curve  starting  at  60°,   or  520°   absolute,    we 

1-    ^1         .  T    1 .08  X  520        ,,     C       0,^0 

have  the  same  mdex ^ —  =  1.22  X  100  =  122  -j-  60  , 

460 

the  starting-point  in  the  scale,  =  182°  the  point  of  intersec- 
tion of  the  60°  heat  curve  with  the  horizontal  line  of  2  at- 
mospheres absolute.     Again  for  the  curve  starting  at  an  initial 

temperature  of   100"  F.    we  have   the   same  index    ^^—^ — 

^  460 

=  1.3  1 5  X  100°  =  1 3 1. 5  +  100    as  the  starting-point  =  231.5, 

the  point  of  meeting  of  the  curve  from  100°  initial  temperature 

with  the  horizontal  line  of  2  atmospheres  absolute.     And  so  on 

throughout  the  diagram. 


144  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

There  is  a  slight  difference  in  the  results  from  the  equations 
of  various  authors  for  the  mean  pressure  from  air  compression. 
The  following  formula  is  different  from  the  one  used  in   Mr. 

Shone'stables— Tables  XVI.,  XVII.:  _^?-  P  f  fi)  ^lUL  -  i1 

n  —  I       LVp/     ji  J 

n  1.406  ^         1  n—  I  rr, 

=  mean  pressure.  =  — - —  =  3.463  and =  .29.    Ihen 

n— I  .406  n 

for  compressing  air  from  atmospheric  pressure  to  60  pounds 

gauge  pressure  P  =  14.7  and  P„  =  74.7.     Then  3.463  X  14.7  X 

//4^j     _  J        _  j^ean  pressure,  which  must  be  worked  out 

as    follows:      The    ratio    of    the    pressures     l^^   =    5.08    log. 

14.7 

0.705864  X  .29  =  0.2047005  index  1.602  —  i  =  .602  X  14.7  X 

3.463  =  30.63,   the  mean    pressure    of    adiabatic   compression 

from  atmospheric  pressure  to  60  pounds  gauge  pressure. 


COMPRESSED    AIR   TABLES. 

In  Table  XVI.  is  given  the  absolute  pressure  in  pounds  per 
-square  inch  from  the  zero  of  pressure  to  3,014.7  pounds  absolute 
in  column  i  on  the  left,  and  the  gauge  pressure  inversely  from 
a  vacuum  to  o  or  atmospheric  pressure,  and  up  to  3,000  pounds 
in  column  8  at  the  right  side  of  the  table. 

Column  2  is  the  absolute  temperature,  Fahrenheit,  of  com- 
pression from  the  absolute  zero  of  temperature  up  to  normal 
temperature  at  atmospheric  pressure,   and   so   on    to    3,014.7, 

and  is   by    the    formula  (^\       X   (461.2  -j-   T)    in    Fahrenheit 

degrees. 

Column  3  =  (column  2  —  461.2)  =  t  —  461.2.°  Fahrenheit 
t  =  column  2. 

Column  4  is  the  absolute  temperature  in  Centigrade  de- 
grees =  t  =  [£|       X  (274 -f-T)  in  Centigrade  degrees. 

Column  5  =  t  —  274  or  column  4  —  274°  C.  Centigrade  t  = 
column  5. 


ADIABATIC    COMPRESSION    AND    EXPANSION. 


145 


Column  6  is  the  adiabatic  compression  of   100  volumes  = 


column   7    X 


or  column  7   X 


col.  2 


.461.2  -\-  T  521.2 

Column  7  is  the  isothermal  compression  of   100  volumes  = 
P  X  100  _  14.7  X   ioo_ 
p  column  I 

The  tables  were  originally  computed  by  Mr.  Shone  in  Eng- 
land up  to  100  pounds  gauge  pressure,  using  the  absolute  tem- 
peratures of  461.2  and  274°  C.  The  error  is  too  small  to  warrant 
a  recomputation,  and  for  symmetry  the  author  has  used  the 
same  formula  for  the  extension  to  3,000  pounds. 


TABLE   XVI. — Pressures,  Temperatures,   and    Volumes    by  Adiabatic  and 
Isothermal  Air  Compression.  (Shone.) 


0  to 
m  EC 

XI  0 

0  ^ 
9  it  i* 

•./I  1>  L. 

Temperature 
from  60°  F. 

at  atmospheric 
pressure. 

0  V-  bo 

«-0 

Volumes  from 

too  at 

atmospheric 

pressure, 

adiabatic. 

Volumes  from 

100  at 

atmospheric 

pressure, 
isothermal. 

a5 
?  i- 

OS. 

I 

2 

3 

4 

5 

6 

7 

8 

0.0 

0.0 

—  461.20 

0.00 

—  274.00 

Infinite. 

Infinite. 

-  14-7 

I 

-f  239.05 

—  222.15 

+  132.81 

-  141. 19 

674.21 

1,470.00 

-  13-7 

2 

292.27 

-  168.93 

162.36 

—  III. 64 

412.16 

735- 

-  12.7 

3 

32S.74 

-  132.47 

182.63 

-  91-37 

309.06 

490. 

-  II-7 

4 

357-34 

-  103.86 

198-52 

-  75-48 

251.96 

367-50 

-  10.7 

5 

381.23 

-  79-98 

211.79 

—  62.21 

215-04 

294. 

-  9-7 

6 

401.93 

-  59-27 

223.29 

-  50.71 

188.93 

245- 

-  8.7 

7 

420.30 

—  40. 90 

233-50 

-  40-50 

169-35 

210. 

-  7-7 

8 

436.  go 

-  24.65 

242.72 

—  31-28 

154-03 

183-75 

-  6.7 

9 

452.08 

—   9.12 

251.16 

—  22.84 

141.67 

163-333 

-  5-7 

ID 

466. 10 

+   4.90 

258.94 

-  15-06 

131-46 

147- 

-  4-7 

II 

479-17 

18.06 

266.21 

-   7-79 

122.86 

133-636 

-  3-7 

12 

491.41 

30.21 

273.02 

—   0.98 

115-50 

122.50 

-  2.7 

13 

502.95 

41-75 

279.41 

+   5.41 

109.12 

113-077 

-  1-7 

14 

513.88 

52.69 

285.49 

11.49 

103-53 

105. 

-  0.7 

14 

521.20 

60.00 

289.56 

15-56 

100.00 

100. 

0. 

15 

531-24 

70.04 

295-13 

21.13 

95-435 

93-631 

I. 

16 

540.84 

79.64 

300.47 

26.47 

91-341 

S8.024 

2. 

17 

550.04 

88.84 

305-58 

31-58 

87.646 

S3-051 

3- 

18 

558.88 

97.68 

310.49 

36.49 

84. 292 

7S.610 

4- 

19 

567-38 

106.18 

315-21 

41.21 

81.231 

74-619 

5- 

20 

575-59 

"4-39 

319-77 

45-77 

78.443 

71.031 

6. 

21 

583-52 

122.32 

324-18 

50.18 

75-842 

67-742 

7- 

22 

591-19 

129.99 

328.44 

54-44 

73-454 

64.758 

8. 

23 

59S.63 

137-43 

332-57 

58.57 

71.240 

62.025 

9- 

24 

605.85 

144-65 

"  336-58 

62.58 

69.180 

59-514 

10. 

25 

612.86 

151.66 

340.48 

66.48 

67-258 

57-198 

II. 

26 

619.68 

158.48 

344-27 

70.27 

65-459 

55-056 

12. 

27 

626.33 

165.13 

347-96 

73-96 

63-773 

53.069 

13. 

28 

7 

632.80 

171.60 

351-56 

77-56 

,  62.187 

51.220 

14. 

146 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


TABLE    XVI.    {Continued). 


29.7 
30.7 

31-7 
32-7 
33-7 
34-7 

35-7 
36-7 
37-7 
38.7 
39-7 
40.7 
41.7 
42.7 
43-7 
44-7 
45-7 
46.7 

47-7 
48.7 

49-7 
50.7 
51-7 
52.7 
53-7 
54-7 
55-7 
56-7 
57-7 
58. 7 
59-7 
60.7 
61.7 
62.7 

63-7 
64.7 

65.7 
66.7 

67.7 
68.7 
69.7 
70.7 

71-7 
72.7 

73-7 
74-7 
75-7 
76.7 

77-7 
78.7 

79-7 
80.7 
81.7 


639.12 
645.29 
651.31 
657.21 
662.97 
668.62 
674-15 
679-57 
684.89 
690. 1 1 
695-23 
700.27 
705.22 
710.08 
714.86 

719-57 
724.20 
728.76 
733-25 
737-68 
742.04 
746.34 
750.58 
754-76 
758.88 
762.95 
766.97 

770.94 
774-86 

77S.73 
782.56 
786.33 
790-07 
793-76 
797.41 
S01.02 
804.59 
808.13 
811.62 
815.08 
81S.50 
821.89 
825.25 
828.57 
831.86 
835.11 

838.34 
841.54 
844-70 
847-84 
850.95 
854.04 
857.09 


177-92 

184.09 
190. II 
196.01 
201.77 
207.42 
212.95 
218.37 

223.69 
228.91 

234-03 
239.07 
244.02 

248.88 

253.66 

258.37 

263.00 

267.56 
272.05 
276.48 

280.84 
285.14 

289.38 
293.56 
297.68 

301.75 
305-77 

309-  74 
313-66 

317-53 
321.36 

325.13 
328.87 
332.56 
336.21 
339.82 
343.39 
346.93 
350.42 
353.88 
357.30 
360.69 
364.05 
367.37 
370.66 

373.91 
377.14 
380.34 
383.50 
386.64 
389-75 
392-84 
395-89 


355-07 
358.49 
361.84 
365-12 
368.32 
371-46 
374-53 
377-54 
380.49 

383-39 
386.24 
389.04 
391-79 
394-49 
397- 1 5 
399-76 
402.33 
404.87 
407-36 
409.82 
412.24 
414-63 
416.99 
4r9-32 
421.60 
423.86 
426.09 
428.31 
430.48 
432.63 
434-76 
436-85 

438-93 
440.98 
443-01 
445-01 
446.99 
448.96 
450.90 
452.S2 
454-72 
456.61 

458.47 
460.32 
462. 14 
463-95 
465-74 
467-52 
469.28 
471.02 
472-75 
474-47 
476.16 


E  ?  c 


81.07 

84-49 
87.84 
91. 12 
94-32 
97.46 
100.53 

103.54 
106.49 
109.39 
112.24 
115.04 

117.79 
120.49 
123.15 
125.76 
128.33 
130.87 
133-36 
135-82 
138.24 
140.63 
142.99 
145-32 
147.60 
149.86 
152.09 
154-30 
156.48 
158-63 
160.76 
162.85 

164-93 
166.98 
169.01 
171.01 
172.99 
174.96 
176.90 
178. 82 
180.72 
182.61 
184.47 
186.32 
188.14 
189.95 
191.74 
193-52 
195.28 
197.02 

198-75 
200.47 
202.16 


•5     ^a=4 


60. 693 

59-283 
57-949 
56.685 

55-485 
54-345 
53-260 
52.225 
51.238 
50.295 
49-392 
48.527 
47.698 
46. 902 
46.136 
45.402 
44-695 
44-013 
43-35^ 
42.722 
42.  no 
41-518 
40.947 
40.393 
39.858 

39.339 
38.836 

38.349 
37.876 
37.416 
36.970 
36.^37 
36.115 
35.706 
35.307 
34.918 
34.540 
34.172 
33.813 
33-462 
33.121 
32.787 
32.462 

32.144 
31.834 
31-531 
31-235 
30-945 
30.662 

30.385 
30.113 
29.84S 
29-5S8 


C   0)  lu  5 

OJ  O  M  «  i) 


49-495 
47-883 
46.372 
44-954 
43-620 

42.363 
41.176 
40.054 
38.992 

37-984 
37.028 
36.118 
35-252 
34.426 
33-638 
32.886 
32.166 
31-478 
30.818 
30.185 

29- 577 
28.994 

28.433 
27.894 

27-374 
26.874 
26.391 
25-926 
25-477 
25-043 
24.623 

24-217 

23-825 

23-445 
23-077 
22.720 

22.374 
22.039 
21.713 

21-397 
21.090 
20. 792 
20. 502 
20.220 
19.946 
19.679 
19.419 
19. 166 
18.919 
18.679 
18.444 
18.216 
17-993 


ADIABATIC    COMPRESSION   AND    EXPANSION. 


H7 


TABLE    XVI.    {Co7itinued). 


O   0) 

Temperature 

from  60°  F. 

at  atmospheric 

pressure. 

Absolute 
temperature. 
Centigrade. 

Temperature 

from  15.56° 

Centigrade. 

Volumes  from 
100  at 

atmospheric 
pressure, 
adiabatic. 

Volume,  from 

100  at 

atmospheric 

pressure, 
isothermal. 

"2i 

a 

I 

2 

3 

4 

5 

6 

7 

8 

82.7 

860.12 

398.92 

477.84 

203.84 

29-334 

17-775 

68. 

83 

7 

863.12 

401.92 

479.51 

205.51 

29.084 

17-563 

69 

84 

7 

866.10 

404.90 

481.17 

207.17 

28.840 

17-355 

70 

85 

7 

869.05 

407.85 

482.81 

208.81 

28.601 

17.153 

71 

86 

7 

871.98 

410.78 

484.43 

210.43 

28.366 

16.955 

72 

87 

7 

874.89 

413.69 

486.05 

212.05 

28.136 

16.762 

73 

88 

7 

877.77 

416.57 

487.65 

213.65 

27.911 

16.573 

74 

89 

7 

880.63 

419.43 

489.24 

215.24 

27.689 

16.388 

75 

90 

7 

883.46 

422.26 

490. 8 1 

216.81 

27.472 

16.207 

76 

91 

7 

S86.28 

425.08 

492.38 

2 18. 38 

27.259 

16.031 

77 

92 

7 

889.07 

427.87 

493.93 

219.93 

27.050 

15.858 

78 

93 

7 

891.84 

430.64 

495-47 

221.47 

26.845 

15.688 

79 

94 

7 

894.  59 

433.39 

496.99 

222.99 

26.643 

15.523 

80 

95 

7 

897.32 

436.12 

498.51 

224.51 

26.445 

15.361 

81 

96 

7 

900.03 

438.83 

500.02 

226.02 

26.251 

15.202 

82 

97 

7 

902.72 

441-52 

501.51 

227.51 

26.060 

15.046 

83 

98 

7 

905.39 

444.19 

502.99 

228.99 

25.872 

14.894 

84 

99 

7 

908.04 

446.84 

504.47 

230.47 

25.687 

14.744 

85 

100 

7 

910.67 

449.47 

505.93 

231.93 

25.506 

14.598 

86 

lOI 

7 

913.28 

452.08 

507.38 

233-38 

25.328 

14.454 

87 

102 

7 

915.88 

454.68 

50S.S2 

234.S2 

25.152 

14-314 

88 

103 

7 

918.46 

457.26 

510.26 

236.26 

24.980 

14.176 

89 

104 

7 

921.02 

459.82 

511.68 

237.68 

24.753 

14.040 

90 

105 

7 

923.56 

462.36 

513.09 

239.09 

24.643 

13.907 

91 

106 

7 

926.08 

464.88 

514.49 

240.49 

24.479 

13-777 

92 

107 

7 

928.59 

467.39 

515.88 

241.88 

24.318 

13-649 

93 

108 

7 

931.08 

469.88 

517.27 

243.27 

24.159 

13-523 

94 

109 

7 

933.56 

472.36 

51S.64 

244. 64 

24.002 

13-400 

95 

no 

7 

936.02 

474.82 

520.01 

246.01 

23.848 

13.279 

96 

III 

7 

938.46 

477.26 

521.37 

247.37 

23.696 

13.160 

97 

112 

7 

940.89 

479.69 

522.72 

248.72 

23.547 

13-044 

98 

"3 

7 

943.31 

482.11 

524.06 

250.06 

23.399 

12.929 

99 

114 

7 

945.71 

484.51 

525.39 

251.39 

23-254 

12.816 

100 

119 

7 

957.44 

496.24 

531.91 

257-91 

22.558 

12.280 

105 

124 

7 

968.91 

507.71 

538.27 

264.27 

21.893 

11.788 

no 

129 

7 

980.11 

518.91 

544.50 

270.50 

21.304 

11-333 

"5 

134 

7 

990. So 

529.60 

550.80 

276.80 

20.822 

10.913 

120 

139 

7 

1,001.22 

540.02 

556.23 

282.23 

20.202 

10.522 

125 

144 

7 

1,011.64 

550.44 

562.02 

288.02 

19.718 

10.159 

130 

149 

7 

1,021.55 

560.35 

567.53 

293.53 

19.245 

9.819 

135 

154 

7. 

1,031.19 

569.99 

572.88 

29S.88 

18.794 

9-502 

140 

159 

7 

1,041.86 

580.66 

578.81 

304.81 

18.391 

9-205 

145 

164 

7 

1,049.95 

588.75 

583.30 

309.30 

17.974 

8-925 

150 

174 

7 

1,068.35 

607.15 

593.53 

319-53 

17.240 

8.414 

160 

184 

7 

1,085.66 

624.46 

603.14 

329.14 

16.576 

7-958 

170 

194 

7 

1,102.59 

641.39 

612.55 

338.55 

15.968 

7- 5  50 

180 

204 

7 

1,118.49 

657.29 

621. 38 

347. 38 

15.403 

7.181 

190 

214 

7 

1,134.23 

673.03 

630.12 

356.12 

14.896 

6.846 

200 

264 

7 

1,205.48 

744.28 

669.71 

395.71 

12.838 

5-553 

250 

314 

7 

1,267.08 

805.88 

703.93 

429.93 

11.355 

4.671 

300 

364 

7 

1,332.96 

871.76 

740. 53 

466. 53 

10.304 

4.030 

350 

414 

7 

1,372.89 

911.69 

762.71 

488.71 

9-334 

3-544 

400 

464 

7 

1,417.70 

956.50 

787.61 

513-61 

8.603 

3-163 

450 

148 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


TABLE    XVI.    {Continued). 


aT  • 

0 

4)       r; 

6  . 

0 

S 

F     0 

11 

<  0. 

III 

<ufc 

Temperatui 

from  6o»  F. 

a  t  atrflosphe 

pressure. 

-Q  at; 
2-0 

Temperatui 

from  15.56' 

Centigrade 

Volumes,  fr 
100  at 

atmospheri 
pressure, 
adiabatic. 

Volume  fro 

100  at 

atmospheri 

pressure, 

isothermal 

bOS 

0?; 

I 

2 

3 

4 

5 

6 

7 

8 

514-7 

1,461.49 

1,000.29 

S11.94 

537-94 

8.008 

2.8^6 

500. 

614.7 

1,538.84 

1.077.64 

854-91 

5S0.91 

7.058 

2  391 

600. 

714-7 

1,607.64 

1,146.44 

893-13 

619.13 

6.340 

2.056 

700. 

814.7 

1,669.92 

1,208.72 

927.73 

653-73 

5-780 

1.804 

800. 

914.7 

1,726.78 

1,265.58 

959-32 

685.32 

5-324 

1.607 

900. 

1,014.7 

1,774-42 

1,313.22 

985-79 

711.79 

4.928 

1.448 

1,000. 

1,214.7 

1.S75-32 

1,414.12 

1,041.84 

767. 84 

4-353 

1. 210 

1 .  200. 

1.414-7 

1,959-71 

1. 498-51 

1,088.73 

8 14- 73 

3.880 

1.032 

1,400. 

1. 614.7 

2,024.71 

1. 563-51 

1,124.84 

S50.S4 

3-534 

0.910 

1,600. 

1.S14.7 

2, 106.63 

1.645-43 

1,170.35 

896-35 

3-274 

o.Sio 

1,800. 

2,014.7 

2, 171.05 

1,709.85 

1,206.14 

932.14 

3-036 

0.729 

2,000. 

2,514-7 

2,315-17 

1.853-97 

1,286.20 

1. 012. 20 

2.594 

0.5S4 

2,500. 

3.014-7 

2,440-41 

1,979-21 

1,355-78 

1. 081. 78 

2.280 

0.487 

3,000. 

In  Table  XVII.  are  given  the  gauge  pressure;  ratios  of  com- 
pression in  volumes  adiabatic  and  isothermal ;  points  of  stroke 
at  gauge  pressure,  adiabatic;  points  of  stroke  at  gauge  pressure, 
isothermal;  the  mean  pressure  at  full  stroke  adiabatic  and  iso- 
thermal, for  compression  from  i  pound  to  3,000  pounds. 

Column  I  =  gauge  pressure,  p  —  P. 

Column  2  =  100  -H  by  the  mean  pressure  at  full  stroke,  adi- 
abatic, as  found  in  column  6,  Table  XVI.,  and  represents  the 
ratio  of  volumes  at  atmospheric  pressure  from  gauge  pressure, 
adiabatic. 

Column  3  =  100-^  by  column  7  in  Table  XVI.,  and  repre- 
sents the  ratio  of  volumes  at  atmospheric  pressure  from  gauge 
pressure,  isothermal. 

Column  4  =  I  -^  by  column  2  in  this  table,  and  represents 
the  point  of  stroke  of  a  piston  at  the  moment  the  gauge  pressure 
is  reached,  adiabatic. 

Column   5  =  I  ^  by  column  3  in  this  table,  and   represents 
the  point  of  stroke  of  a  piston  at  the  moment  the  gauge  press- 
ure is  reached,  isothermal. 
i+H 


Column  6  =  p  X 


R 


—  P,  in  which  R  is  the  ratio  of  the 


ADIABATIC    COMPRESSION    AND    EXPANSION. 


149 


adiabatic  compression   in  column  2   of  this  table  and   H  —  the 
hyperbolic  logarithm  of  the  ratio  R  in  column  2  of  this  table. 

Column  7  =  p  X    ^"^    -  _  P;  in  which  R  is  the  ratio  of  iso- 
R 

thermal  compression  found  in  column  3,  and  equals  ^  or  absolute 

pressure  divided  by  the  normal  pressure.      H  =  the  hyperbolic 

logarithm  of  the  ratio  of  isothermal  compression  "  in  column  3 

of  this  table. 

In  the  absence  of  tables  of  hyperbolic  logarithms,  the  com- 
mon logarithm  of  a  number  X  2.302585  =  hyperbolic  logarithm. 

TABLE  XVII. — Gauge  Pressures,  Ratios  of  Compression,  Points  of  Stroke, 
AND  Mean  Pressure  for  Full  Stroke  in  Air  Compression.         (Shone.) 


0 

0 

0   .     J. 

•w  ■JJ  !--  (U  "3           " 

u  0 

£0.2 

<o  It, 

3  m 

0    dJ  iL  ■-■ 

-r;  c  g- «  (U     -re 

tan  cs 

^  U  4)  in  g 

'0  ■   "^  M  "" 

n!  M 

3. 

^1 

UH  QJ^  TO 

5;  DS-^ 

a5o 

n! 

OS  -       c 

0           --H 

ctf 

I 

2 

3 

4 

5 

6 

7 

I 

1.0478 

1.0680    0 

954 

0.936 

0.978 

0.967 

2 

1.0948 

I.I36I 

913 

.880 

1^937 

1.874 

3 

1. 1409 

1. 2041 

876 

.831 

2.846 

2.680 

4 

1. 1864 

1. 2721 

843 

.786 

3.805 

3-513 

5 

I. 2310 

1. 3401 

812 

-746 

4.615 

4-303 

6 

1.2748 

1.4078 

784 

.710 

5.419 

5-055 

7 

1-3185 

1.4762 

758 

.677 

6.326 

5-762 

8 

1. 3614 

1-5442 

735 

.648 

7.  lOI 

6.347 

9 

1-4037 

1. 6122 

712 

.620 

7.865 

7.000 

10 

1-4455 

1.6803 

692 

•  595 

8-737 

7.626 

II 

1.4868 

1-7483 

673 

■  572 

9-479 

8.226 

12 

1.5277 

I.SI64 

655 

•  551 

10. 21 1 

8.802 

13 

1.56S1 

1.8844 

638 

■531 

10.934 

9.280 

14 

1.6081 

1-9524 

622 

-512 

11.647 

9.817 

15 

1.6476 

2.0204 

607 

-495 

12.353 

10.336 

16 

1.6868 

2.0884 

593 

■479 

13.049 

10.S37 

17 

1-7257 

2.i5f)5 

579 

.464 

13-738 

11.320 

18 

1. 7641 

2.2245 

567 

-450 

14-314 

11.723 

19 

1.8023 

2.2925 

555 

-436 

14.990 

12.180 

20 

I. 8401 

2.3605 

543 

.424 

15-657 

12.623 

21 

1.S776 

2.42S6 

533 

.412 

16.317 

13.052 

22 

1. 9148 

2.4966 

522 

.401 

16.870 

13-470 

23 

I-9517 

2.5646 

512 

-390 

17.516 

13.818 

24 

1-9883 

2.6327 

503 

.380 

18.157 

14.215 

25 

2.0246 

2.7007 

494 

•  370 

18.695 

14.602 

26 

2.0607 

2.7687' 

48  5 

.361 

19-324 

14.976 

27 

2.0965 

2.8367 

477 

•353 

19.946 

15-344 

28 

2.1321 

2.9048 

469 

•  344 

20.470 

15.651 

29 

2.1675 

2.9728 

461 

•  336 

21.081 

16.002 

30 

2.2025 

3.0408 

454 

•329 

21.597 

16.345 

150  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

TABLE    XVII.   {Continued). 


0 

.2 
<*.*  "tl  t.«  oT  0 

0   .     ^ 

fl?  0 

a7  rt 

ar_. 

Gauge 

pressur 

Ratio  0 

volume  s 

atmosphe 

pressuri 

adiabati 

1 

Ratio  0 

volume  i 

atmosphe 

pressun 

isotherm 

Point 

gauge 
pressviri 
adiabati 

Point 

0)  •„  p 

ill 

Mean 

pressur 

at  full  strc 

adiabatii 

Mean 

pressur 

at  full  strc 

isotherm 

I 

2 

3 

4    i 

5 

6 

7 

31 

2.2374 

3.10SS 

447 

.322 

22.199 

16.679 

32 

2.2721 

3.1769 

440 

-315 

22.704 

17.006 

33 

2.3065 

3-2449 

434 

.308 

23.295 

17.281 

34 

2.3407 

3-3129 

427 

.302 

23-794 

17-594 

35 

2.3747 

3-3S10 

421 

296 

24.288 

17-903 

36 

2.40S6 

3-4490 

415 

290 

24.865 

18.204 

37 

2.4422 

3-5170 

409 

284 

25-352 

18.500 

38 

2.4757 

3-5850 

404 

279 

25-923 

18.790 

39 

2.5089 

3-6531 

399 

274 

26.402 

19.032 

40 

2.5420 

3.7211 

393 

269 

26.87S 

19.311 

41 

2.5749 

3-7891 

388 

264 

27-350 

19.586 

42 

2.6076 

3-8571 

383 

259 

27-905 

19.855 

43 

2.6402 

3.9252 

379 

255 

28.370 

20.118 

44 

2.6726 

3-9932 

374 

250 

28.834 

20.342 

45 

2.7049 

4.0612 

370 

246 

29.295 

20.598 

46 

2.7370 

4-1293 

365 

242 

29-833 

20. 849 

47 

2.7689 

4-1973 

361 

238 

30.285 

21.096 

48 

2.8007 

4-2653 

357 

234 

30.737 

21-339 

49 

2.8323 

4-3333 

353 

231 

31-187 

21-544 

50 

2.8638 

4.4014 

349 

227 

31.632 

21.780 

51 

2.8952 

4.4694 

345 

224 

32.154 

22.012 

52 

2.9264 

4-5374 

342 

220 

32.594 

22.040 

53 

2.9575 

4.6054 

338 

217 

33-033 

22.465 

54 

2.98S4 

4-6735 

335 

214 

33-468 

22.656 

55 

3-0193 

4-7415 

331 

211 

33-901 

22.873 

56 

3.0499 

4-8095 

328 

208 

34-330 

23.089 

57 

3.0805 

4-8776 

325 

205 

34-758 

23.301 

58 

3.  mo 

4-9456 

321 

202 

35-183 

23.511 

59 

3-1413 

5.0136 

318 

199 

35-607 

23.688 

60 

3-1715 

5.0S16 

315 

197 

36.027 

23.892 

61 

3.2016 

5-1497 

312 

194 

36.448 

24.092 

62 

3-2315 

5-2177 

309 

192 

36.864 

24.292 

63 

3.2614 

5-2857 

307 

1S9 

37-277 

24-487 

64 

3.2911 

5-3537 

304 

187 

37.690 

24-653 

65 

3.3208 

5.4218 

301 

184 

38.098 

24.844 

66 

3-3503 

5.4898 

298 

182 

38.509 

25-033 

67 

3-3797 

5-5578 

296 

180 

38-914 

25-219 

68 

3-4091 

5-6259 

293 

178 

39-317 

25-403 

69 

3-4383 

5-6939 

291 

176 

39. 720 

25-559 

70 

3-4674 

5-7619 

288 

174 

40. 1 2 1 

25-738 

71 

3-4964 

5-8299 

286 

172 

40.518 

25.916 

72 

3-5253 

5.8980 

284 

170 

40.913 

26.093 

73 

3-5541 

5.9660 

281 

168 

41-237 

26. 264 

74 

3-5829 

6.0340 

279 

166 

41.631 

26.411 

75 

3.6115 

6. 1020 

277 

164 

42.021 

26.582 

76 

3.6400 

6. 1 701 

275 

162 

42.411 

26.750 

77 

3.6685 

6.2381 

273 

160 

42.797 

26.916 

78 

3.6969 

6.3061 

271 

159 

43-182 

27.079 

79 

3-7251 

6.3742 

268 

157 

43-566 

27.218 

80 

3-7533 

6.4422 

266   1 

155 

43-882 

27-379 

81 

3-7814 

6.5102 

264 

154 

44. 260 

27-538 

82 

3.8094 

6.5782 

263 

152 

44-639 

27.695 

83 

3-S373 

6.6463 

261 

150 

45-017 

27-851 

84 

3-8652 

6.7143 

259 

149 

45-393 

27-983 

ADIABATIC    COMPRESSION   AND    EXPANSION. 
TABLE    XVII.    {Continued). 


151 


<D 

0 

0 

■t'  'S  E  <u  * 

"i   (iT  cj 

=s   a,"3 

6 
"0  u 

(U  I- 

0  "  5;  1-  -M 

.2  P  &S.D 

j_i  •-'  t/:  O)  fr; 

n  !>•=  S  F 
°  E  Q.  •T^  ~ 

•^  c  jr  ^  oj 

*j  (u  (u  i-'r; 

■5  p  e;  M  .D 

^  m  «  I.  c 

0  2  rt  S  ^ 

2  M  "^.Q 

u  c  r- 
0  «1  ^  D 

1^  3  0  a;;S 

oi  !^  d  0)-^ 

eu  i^  S,  ai  .S 

ac  0 

""S 

ts  ■" 

0 

0          .-H 

ji 

Oj"^ 

I 

2 

3 

4 

5 

6 

7 

85 

3.8929 

6.7823 

•  257 

.147 

45-  700 

28.136 

86 

3.9260 

6.8503 

•  255 

.146 

46-137 

28.286 

87 

3.9482 

6.91S4 

•  253 

•  145 

46-443 

28.436 

88 

3-9757 

6.9864 

.252 

-143 

46.813 

28.584 

89 

4.0032 

7-0544 

.250 

.142 

47-115 

28.709 

90 

4.0306 

7.1224 

.248 

.140 

47-482 

28.855 

91 

4-0579 

7-1905 

.246 

■  139 

47-487 

28.999 

92 

4.0S51 

7-2585 

.245 

-138 

48.209 

29.141 

93 

4. 1122 

7-3265 

•  243 

.136 

48.507 

29.282 

94 

4-1393 

7-3946 

.242 

•  135 

48.869 

29.401 

95 

4.1663 

7.4626 

.240 

-134 

49.227 

29.541 

96 

4.1932 

7.5306 

-238 

-133 

49-522 

29.678 

97 

4.2201 

7.5986 

-237 

.132 

49-878 

29.813 

98 

4. 2469 

7.6667 

-235 

.130 

50.234 

29.948 

99 

4.2736 

7-7347 

•  234 

.129 

50.525 

30.063 

100 

4-3003 

7.8027 

-233 

.128 

50.878 

30-195 

105 

4-433 

8.143 

.225 

.123 

52-451 

30.824 

no 

4-567 

8-483 

.219 

.118 

54-034 

31.427 

115 

4-693 

8-823 

.213 

-113 

55.662 

32.004 

120 

4.802 

9.163 

.208 

.109 

57-351 

32.552 

125 

4-950 

9-503 

.202 

.105 

58.656 

33.091 

130 

5-071 

9-843 

.197 

.102 

60.153 

33.615 

135 

5-195 

10.184 

.192 

.098 

61.587 

34. 102 

140 

5.328 

10.524 

.188 

•095 

62.650 

34.649 

145 

5-437 

10.864 

.184 

.092 

64.199 

35.062 

150 

5-563 

11.204 

.179 

.089 

65.706 

35.368 

160 

5.800 

11.884 

.172 

.0S4 

68.369 

36.312 

170 

6.033 

12.565 

.166 

.080 

70.926 

37.293 

180 

6.263 

13-245 

.159 

.076 

73.491 

37.966 

190 

6.492 

13-925 

•  154 

.072 

76.797 

38.706 

200 

6.713 

14-605 

.149 

.068 

78.189 

39.463 

250 

7.789 

18.007 

.128 

•055 

89.035 

42.475 

300 

8.806 

2 1 . 408 

•  113 

-047 

98.780 

44-998 

350 

'  9-705 

24.808 

.103 

.040 

108.276 

47.189 

400 

10.713 

28.210 

•093 

-035 

115.889 

49-039 

450 

11.623 

31.612 

.086 

.032 

123.594 

50.776 

500 

12.487 

35.014 

.080 

.029 

131.423 

52.262 

600 

14.168 

41.816 

.070 

.024 

143.646 

54-822 

700 

15-773 

48.618 

.063 

.021 

155.541 

57-055 

800 

17.301 

55-422 

.058 

.018 

166.163 

58.948 

900 

18.783 

62.224 

•  053 

.016 

176.929 

60.671 

1,000 

20.292 

69.027 

-049 

.014 

185.703 

62.214 

1,200 

22.972 

82.632 

-043 

.012 

203.824 

64.862 

1,400 

25-773 

96.238 

■  039 

.010 

219.442 

67.069 

1,600 

28. 296 

109.843 

•035 

.009 

232.994 

68.941 

1,800 

30. 543 

123.449 

•033 

.008 

247.705 

70.772 

2,000 

32-938 

137-054 

.030 

.007 

260. 105 

72  133 

2,500 

38-550 

171.068 

.026 

.006 

289.327 

75.326 

3,000 

43-859 

205.081 

.023 

.005 

313.902 

78.152 

Chapter  X. 


THE  COMPRESSED  AIR 
INDICATOR  CARD 


THE    COMPRESSED    AIR    INDICATOR   CARD. 

The  theoretical  conditions  of  air  compression  and  expan- 
sion may  be  diagrammatically  expressed  to  represent  both  the 
theoretical  and  the  practical  lines  of  compression  and  expansion, 
with  the  difference  that  the  theoretical  lines  or  curves  may  be 
computed  from  the  known  law  of  thermodynamics,  but  the 
practical  lines  or  curves  must  be  found  and  based  on  the  heat- 
absorbing  element  of  the  compressor,   which   is  an   uncertain 


G  Atmos. 
-^J  Vacuum 

Fig.  46.— compressed  air  indicator  card. 

amount  depending  much  on  the  velocity  of  the  pistons,  or  rather 
the  velocity  of  transmission  through  the  compressor  and  the  de- 
gree of  absorption  of  heat  by  the  walls  of  the  cylinder. 

Referring  to  Fig.  46  we  have  the  adiabatic  or  heat  line  A-B, 
which  represents  the  work  done  if  there  were  no  cooling  effect 
in  the  cylinder,  the  line  A-C  representing  the  actual  work  done 
in  the  cylinder,  and  the  isothermal  or  constant  temperature  line 
A-D,  which  is  the  line  the  indicator  would  make  if  all  the  heat 
generated  could  be  carried  off  during  the  work  of  compression. 

This  latter  condition  does  not  exist  in  our  high-speed  ma- 
chines of  to-day,  but  one  can  imagine  it  to  exist  in  a  machine 
where  the  piston  travels  slow  enough  to  allow  all  the  heat  to  be 
carried  off  by  the  water  jacket  or  by  radiation.  In  following  the 
movement  of  the  piston  in  the  cylinder,  suppose  it  starts  at  A, 


156  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

the  cylinder  then  being  full  of  free  air,  and  moves  to  the  right; 
the  pressure  in  the  cylinder  at  any  point  is  represented  on  line 
A-C.  When  the  piston  reaches  C,  it  has  compressed  the  air  to 
the  receiver  pressure,  and  it  must  then  push  the  compressed  air 
out  through  the  discharge  valves  into  the  receiver.  Owing  to 
the  weight  of  the  discharge  valves  and  the  tension  of  the  springs 
holding  them  to  their  seats,  the  pressure  in  the  cylinder  reaches 
a  few  pounds  above  the  receiver  pressure  before  the  valves  open, 
as  shown  at  £,  and  there  gradually  drops  to  the  receiver  press- 
ure at  the  end  of  stroke,  the  irregularities  in  the  line  being  due 
to  the  fluttering  of  the  discharge  valves  and  the  vibration  of  the 
indicator  arm. 

The  piston,  having  reached  the  end  of  stroke,  comes  to  a 
standstill  while  the  crank  is  passing  the  dead  centre ;  and  as  the 
current  of  air  that  held  the  discharge  valves  open  in  passing  out 
of  the  cylinder  has  ceased,  the  discharge  valves  close  by  the 
tension  of  the  springs  back  of  them.  The  piston  now  starts  to 
recede^ — the  air  under  pressure  that  was  left  in  the  cylinder 
due  to  the  clearance  space  expanding  until  it  becomes  atmos- 
pheric pressure  at  F,  when  the  inlet  valves  open  and  the  cylin- 
der is  filled  with  free  air.  If  the  indicator  line  follows  along 
the  atmospheric  line,  we  know  that  the  inlet  area  is  not  re- 
stricted and  we  are  getting  a  volume  of  free  air  at  atmospheric 
pressure  represented  by  the  travel  of  piston  from  F  to  A,  this 
representing  the  actual  free  air  capacity  of  the  compressor. 
The  volume  between  G  and  F  representing  the  air  contained 
in  the  clearance  space,  expanded,  is  lost  as  far  as  the  capacity  of 
the  compressor  is  considered ;  and  although  this  air  required 
work  in  compressing  it  to  75  pounds  pressure,  it  has  given  out 
its  work  in  expanding,  helping  to  compress  the  air  on  the  other 
side  of  the  piston. 

The  only  loss  in  work  due  to  the  clearance  space  is  that  re- 
sulting from  the  small  amount  of  cooling  that  the  confined  air 
has  been  subjected  to,  its  volume,  when  hot,  having  been  a  trifle 
more  and  having  required  more  work  to  compress  it;  but  this  is 


THE   COMPRESSED    AIR    INDICATOR    CARD.  157 

rarely  taken  into  account.  We  thus  see  that  the  clearance 
space  in  the  cylinder  is  not  a  loss  of  power,  but  a  loss  of  capac- 
ity, which  is  allowed  for  by  deducting  anywhere  from  3  to  6  per 
cent  of  the  cylinder  volume,  according  to  the  design  of  the  air 
cylinder  and  the  length  of  stroke  of  same — it  being  evident 
that  the  longer  the  stroke  for  the  same  size  cylinder  the  less 
will  be  the  percentage  of  clearance.  On  some  indicator  cards  it  is 
noticed  that  the  intake  air  pressure  falls  below  the  atmospheric 
line,  showing  that  the  air  inlet  is  restricted,  or,  as  is  common 
on  air  cylinders  having  poppet  inlet  valves  closed  by  a  spring, 
the  tension  of  the  spring  when  the  piston  is  moving  slow  at  the 
end  of  the  stroke  will  close  the  valves  before  the  piston  has 
completed  its  stroke,  so  that  when  the  end  of  stroke  is  reached 
a  partial  vacuum  is  formed  in  the  cylinder.  Where  these  de- 
fects exist,  the  piston  must  travel  a  distance  of  A-O  before  the 
atmospheric  line  is  reached,  and  the  volume  of  the  cylinder 
would  be  0-F,  instead  of  A-F,  making  the  6-per-cent  allowance 
for  clearance  necessary,  while  2  to  3  per  cent  should  be  suffi- 
cient on  a  well-designed  compressor. 

The  temperature  of  the  air  at  75  pounds  gauge  pressure 
without  any  cooling  is  419°,  although  this  is  somewhat  lower  in 
the  cylinder,  due  to  the  jacket  cooling;  and  from  actual  readings 
on  thermometers  placed  in  the  discharge  pipe  close  to  the  cylin- 
der, the  temperature  is  from  300°  to  360°,  according  to  the  size 
and  speed  of  the  compressor. 

Referring  again  to  Fig.  46  we  have  the  volume  C-K-A-G, 
representing  about  25  per  cent  of  the  free  air  volume  at,  say, 
320°  temperature,  to  put  into  the  receiver  at  each  stroke  of  the 
compressor  piston.  As  the  receiver  is  anywhere  from  10  to  20 
feet  from  the  compressor,  and  as  it  has  a  large  surface  exposed 
for  radiation,  its  temperature  will  be  considerably  less  than 
that  of  the  air  leaving  the  cylinder,  which  will  consequently  be 
cooled  and  reduced  in  volume ;  and  as  the  air  is  generally  used 
a  considerable  distance  from  the  compressor,  it  will  have 
reached  atmospheric  temperature  by  the  time  it  is  used,  and  the 


158  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

original  volume  C-K-N-G,  when  leaving  the  cylinder,  will  have 
shrunk  to  D-K-L-G  by  the  time  it  is  used,  being  then  only 
■^f  of  what  it  would  have  been,  had  the  air  been  used  hot  di- 
rectly as  it  left  the  compressor.  So  that  the  actual  loss  by 
shrinkage  within  the  cylinder  of  a  compressor  of  the  best  con- 
struction may  be  no  more  than  from  2  to  3  per  cent  of  the  vol- 
ume together  with  the  clearance  of  an  average  from  all  causes, 
say  of  3  per  cent,  which  with  the  cooling  by  transmission  brings 
the  volume  of  free  air  entering  the  compressor  to  about  16  per 
cent  at  75  pounds  gauge  pressure. 


THE    MEAN    PRESSURE    OF   AN    INDICATOR    CARD. 

The  indicator  is  the  proper  instrument  for  investigating  the 
internal  work  of  compressing  air,  and  the  indicator  card  is  the 
best  representation  of  the  work  of  the  compressor. 

In  Fig.  47  is  shown  a  facsimile  of  an  indicator  card  from  a 
22  by  30  inch  air  cylinder  running  at  50  revolutions  per  minute 
and  delivering  air  into  a  receiver  at  80  pounds  per  square  inch 
pressure.  It  will  be  seen  that  the  sum  of  all  the  pressures  in 
the  divisions  of  the  card  amount  to  541,  which  divided  by  the 
number  of  division  measurements,  15,  =  36  pounds  per  square 
inch  as  the  mean  pressure  of  the  whole  stroke.  The  usual 
practice  is  to  divide  the  card  into  ten  parts,  but  we  have  used 
fifteen,  which  gives  a  more  satisfactory  result;  and  even  twenty 
parts  gives  a  truer  mean  pressure.  By  comparing  the  mean 
pressure  from  the  indicator  card  with  the  mean  theoretical 
pressure  in  column  6  of  Table  XVII.,  which  for  80  pounds  gauge 
pressure  is  43.88  pounds,  it  will  be  seen  that  a  difference  of  7.88 
pounds  exists,  which  is  due  to  the  absorption  of  heat  by  the 
walls  of  the  air  cylinder,  clearance,  and  a  possible  leakage.  It 
will  also  be  seen  that  the  isothermal  mean  pressure  in  column 
7,  Table  XVII.,  for  80  pounds  gauge  pressure  is  theoretically 
27.37  pounds,  and  the  difference  from  the  mean  pressure  of  the 
indicator  card  is  8.63  pounds,  so  that  with  these  figures  the  loca- 


THE   COMPRESSED   AIR    INDICATOR   CARD. 


159 


tion  of  the  terminals  of  the  adiabatic  and  isothermal  curves  can 
be  established,  and  from  which  the  actual  efficiency  of  the  com- 
pressor can  be  found  for  the  speed  at  which  it  was  running 
when  the  card  was  taken.  For  this  card  the  speed  was  50  revo- 
lutions per  minute,  which  was  but  two-thirds  the  speed  due  to  its 
full  work.  It  maybe  noted  here  that  the  mean  pressure  due  to 
287 


the  curve  only,  is 


II. 8 


24.3  pounds,  and  that  the  mean  press- 


ure for  isothermal  compression  due  to  the  curve  only  for  80 
pounds   terminal    is   27.37 —  .  1 55  X  80  =  14.97   pounds.     The 


Fig.  47.- the  indicator  card. 

difference  24.30  —  14.97  =  9.33  represents  the  difference  of  the 
terminals  of  the  actual  and  the  isothermal  curves  in  pressure 
terms.  The  mean  pressure  due  to  a  perfect  adiabatic  compres- 
sion, by  Table  XVII.,  column  6,  for  80  pounds  gauge  pressure 
would  be  43.88  pounds,  and  for  isothermal  compression  27.37  as 
per  column  7,  same  table;  their  difference  16.51—9.33  =  7.18, 
the  mean  of  which  is  35.62,  a  little  less  than  shown  on  the 
measured  card.  This  indicates  the  fact  that  the  compressor  by 
its  slow  speed  absorbed  less  than  one-half  the  heat  generated 
by  compression  as  indicated  by  the  numbers  9.33  and  7.18;  on 
the  other  hand  the  indicator  card  shown  at  Fig.  46  appears  to 


i6o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


have  been  taken  from  a  quick  or  normal  speed  of  the  compres- 
sor, and  shows  the  actual  compression  curve  considerably  above 
the  mean,  only  about  one-third  of  the  heat  of  compression  being 
absorbed  during  the  stroke  of  compression. 

The  falling-oif  of  the  line  of  delivery  at  the  top  of  the  cards 
indicates  in  part  the  absorption  of  heat  from  the  air  and  the 
relief  of  the  valve  opening  to  the  receiver  pressure,  which  is 
always  found  to  be  from  one  to  three  pounds  less  than  the  com- 
pression pressure  on  the  card. 

THE    STEAM   AND    AIR    CARD. 

In  Fig.  48  is  illustrated  a  combined  steam  and  air  indicator 
card,  showing  the  reason  for  and  answer  to  the  oft-repeated  ques- 
tion as  to  how  it  is  possible  to  compress  air  to  80  or  100  pounds 


Fig.  48.— steam  and  air  card. 


pressure  with  60  pounds  or  less  steam  pressure  with  equal-sized 
cylinders.  The  reason  is  plainly  shown  in  the  comparative 
areas  of  the  steam  and  air  card,  and  from  the  computed  mean 
engine  pressure  of  each  from  actual  measurement  for  pressures 
which  show  enough  excess  of  power  in  the  steam  card  to  over- 
come the  friction  of  the  compressor  and  give  it  the  required 
motion.  The  M.  E.  P.  of  the  air  card  divided  by  the  M.  E.  P. 
of  the  steam  card  shows  90  per  cent  efficiency,  or  that  10  per  cent 
of  the  power  of  the  steam  used  has  been  absorbed  in  the  mov- 
ing parts  pertaining  to  both  cylinders.  In  many  of  the  best 
designed  compressors,  the  difference  shown  in  the  steam  and 
air  cards  has  ranged  from  5  to  6  per  cent.     What  is  made  up  in 


THE    COMPRESSED    AIR    INDICATOR    CARD.  l6l 

the  air  card  by  high  pressure  is  represented  in  the  steam  card 
by  greater  volume.  It  will  be  noticed  that  the  central  points  of 
pressure  in  each  card  do  not  coincide,  and  that  the  minimum 
pressure  in  the  steam  cylinder  occurs  at  the  moment  of  maxi- 
mum pressure  in  the  air  cylinder.  This  condition  would  check 
the  operation  of  an  air  compressor  but  for  the  retaining  power  of 
the  fly-wheel,  the  momentum  of  which  carries  the  air  piston  to 
the  end  of  its  stroke,  thus  equalizing  the  motion  of  all  the  mov- 
ing parts  of  a  compressor.  This  condition  is  due  to  the  high- 
pressure  impulse  of  the  steam  piston  being  transmitted  to  the 
fly-wheels,  in  which  it  is  stored  and  given  out  during  the  high- 
pressure  work  of  the  air  piston. 

The  fly-wheel  does  more  than  this :  its  weight  gives  uni- 
formity of  motion  to  the  compressor,  so  much  to  be  desired  in  a 
continuously  moving  machine. 


Chapter  XI. 


ACTUAL  WORK  OF  THE 
COMPRESSOR 


.63 


ACTUAL  WORK   OF    THE  COMPRESSOR. 

No  compressor  of  the  piston  type  of  modern  construction  can 
produce  the  conditions  required  by  the  theoretically  adiabatic 
or  isothermal  lines  in  columns  6  and  7  in  Table  XVII.  The 
mean  pressure  practically  is  always  between  these  two  lines,  and 
in  most  compressors  runs  nearer  to  the  adiabatic  than  to  the 
isothermal  line ;  and  also  varies  in  the  same  compressor  with 
the  speed  and  the  efficiency  of  the  water-jacket.  In  a  high- 
speed compressor  the  mean  pressure  nears  the  adiabatic  line, 
while  with  a  slow  speed  and  rapid  cold-water  circulation  in  the 
jacket  it  is  possible  to  obtain  a  mean  less  than  half  the  dif- 
ference of  the  adiabatic  and  isothermal  curves,  time  being 
a  considerable  element  in  fixing  the  curve  of  compression. 
It  is  only  with  compressors  of  the  old  Dubois  and  Francois 
type  with  water  injection  and  water-filled  clearance,  and  the 
hydraulic  compressor  of  Sommeiller,  that  the  isothermal  line 
was  nearly  or  quite  reached ;  and  later  with  the  hydraulic  pit 
compressors  of  the  Frizell  and  Taylor  type  has  it  been  possible 
to  reach  the  full  line  of  isothermal  compression,  and  even  under 
differences  in  temperature  of  the  air  and  water,  to  produce  a 
condition  of  compression  of  air  and  its  delivery  below  the  at- 
mospheric temperature. 

In  Table  XVIII.  we  have  endeavored  to  show  the  practical 
operation  of  air  compression  with  a  single  compression  from  5 
to  120  pounds  by  intervals  of  5  pounds  gauge  pressure,  with  an 
assumed  absorption  of  four-tenths  of  the  heat  of  compression. 
In  column  2  of  the  table  the  mean  pressure  for  full  stroke  is 
obtained  from  six-tenths  of  the  difference  between  the  isother- 
mal and  adiabatic  mean  pressures  found  in  columns  6  and  7, 
Table  XVII.,  added  to  the  isothermal  mean  pressure  in  column  7. 


1 66 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


TABLE  XVIII.— Oi-  THK  Mean  Pressure  and  the  Relative  Load  of  Com- 
pression AND  Delivery  in  Terms  of  the  Mean  Pressure  of  the  Whole 
Load,  for  the  Actual  Operation  of  a  Compressor  at  Medium  Speed 
with  Ample  Water  Circulation  in  the  Jacket  of  Cylinder  and  Heads, 
due  to  the  Estimated  Absorption  of  y-'jy  of  the  Heat  of  Compression 
from  6o    F. 


Gauge 

Meau 

Pressure  due 
to  del  iverv 

Mean 
compression  of 

Point 
of  stroke  when 

Temperature 
of 

pressure, 
pounds. 

pressure  for 
full  stroke. 

in  part  of  the 
whole  stroke. 

curve 
in  part  of  the 
whole  stroke. 

pressure  is 
reached. 

discharge 
from  60°  F. 

I 

2 

3 

4 

5 

6 

5 

4-49 

3-92 

0.57 

0.785 

87'^ 

lO 

8.29 

6.53 

I 

76 

.665 

112 

15 

11-54 

8-43 

3 

II 

.562 

130 

20 

14.44 

9.90 

4 

54 

-495 

148 

25 

17-05 

II. 10 

5 

95 

-444 

164 

30 

19.49 

12.12 

7 

37 

.404 

178 

35 

21.73 

12.98 

8 

75 

-371 

192 

40 

23-85 

13.72 

10 

13 

-343 

204 

45 

25.81 

14.40 

II 

41 

.320 

216 

50 

27.69 

15-00 

12 

69 

.300 

227 

55 

29.48 

15-56 

13 

93 

.283 

238 

60 

31-17 

16.38 

14 

79 

•  273 

247 

65 

32-79 

16.64 

16 

15 

.256 

257 

70 

34-36 

17.42 

16 

94 

.242 

266 

75 

35.84 

18.52 

17 

32 

.231 

275 

80 

37-28 

19.60 

17 

68 

.221 

283 

85 

38.67 

20.57 

18 

10 

.213 

292 

90 

40.03 

21.67 

18 

36 

.204 

300 

95 

41-35 

22.64 

18 

71 

.197 

3~-7 

100 

42.60 

23-70 

18 

90 

.189 

314 

105 

43.80 

24.48 

19 

32 

.184 

321 

no 

44.99 

25-33 

19 

66 

.178 

329 

115 

46.20 

26.30 

19 

90 

.173 

335 

120 

47-43 

27.27 

20 

16 

.168 

342 

Column  3  is  obtained  from  six-tenths  of  the  difference  of  the 
points  of  stroke  in  columns  4  and  5,  Table  XVII.,  for  adiabatic 
and  isothermal  compression,  added  to  the  point  of  stroke  for 
isothermal  compression,  column  5,  and  the  sum  multiplied 
by  the  pressure  in  column  i,  which  is  equal  to  the  part  of  the 
whole  mean  pressure  due  to  delivery.  Column  4  is  equal  to 
the  part  of  the  whole  mean  pressure  due  to  the  curve  of  com- 
pression only,  and  is  found  by  column  2  —  column  3  =  column 
4.  Column  5  is  the  assumed  point  of  stroke,  found  by  adding 
six-tenths  of  the  difference  of  the  adiabatic  and  isothermal  points 
of  stroke  in  columns  4  and  5  in  Table  XVII.,  and  the  isother- 
mal point  of  stroke  in  colum.n   5  of  the  same  table.     Column 


ACTUAL    WORK    OF   THE    COMPRESSOR. 


167 


6  represents  the  temperature  of  the  air  from  the  compressor 
delivery  valves,  when  four-tenths  of  the  heat  of  compression 
from  60°  F.  has  been  absorbed  by  the  cooling  appliances  and 
wails  of  the  cylinder,  and  is  obtained  from  column  3,  Table 
XVI.,  —60°  F.  X  31J  of  this  increase  of  temperature  and  60° 
added  to  the  product. 


THE    WORK    OF    AIR    COMPRESSION. 

It  is  often  desired  to  find  the  amount  of  mechanical  work 
which  air  receives  during  compression  only,  and  also  the  work 
of  the  whole  stroke  of  a  piston  for  isothermal  and  adiabatic  com- 
pression ;  we  therefore  illustrate  in  Fig.  49  an  isothermal  in- 
dicator card  with  the  area 
of  compression  only, 
shaded  to  give  to  the  eye 
a  comprehensive  compari- 
son with  the  work  of  de- 
livery shown  by  the  rec- 
tangle following  the  point 
of  compression  stroke. 

The  curve  of  compres- 
sion as  represented  in  the 

diagram  is  that  of  a  hyperbola,  one  of  the  properties  of  which  is 
that  the  areas  of  the  rectangles  contained  by  the  horizontal  and 
vertical  ordinates  from  the  several  points  in  the  curve  as  at  P, 
P\  P\  7",  are  always  the  same,  that  is,  all  the  pressures  and 
volumes  products  (p,  v),  absolute  rectangles,  are  equal  in  area; 
as  further  explained  in  the  article  on  isothermal  compression. 
Then  for  the  work  of  compression  from  atmospheric  or  normal 
pressure  (14.7)  to  any  desired  pressure,  the  increments  of  com- 
pression to  the  end  of  the  stroke  become  a  numerator  in  the  frac- 
tion of  the  whole  stroke,  and  their  quotient  becomes  the  ratio  of 
which  the  hyperbolic  logarithm  multiplied  by  the  pressure  of 
the   normal   atmosphere  upon  a  square     foot  equals    the   foot- 


'/i      Vs      'A  ^^"^     o 

Fig.    49.— ISOMETRICAL  CARD. 


l68  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

pounds  required  for  compression.  Thus,  for  compressing  one 
cubic  foot  of  air  from  atmospheric  pressure  to  two  atmospheres, 

we  have    ^  =  "-^-■-     =  2,  the  hyperbolic  logarithm  of  which   is 
P        14.7 

.6931  X  2,116.8  =   1,467.15    foot-pounds  per  cubic  foot  of  air 

compressed    isothermally   from    atmospheric   pressure    to    14.7 

pounds  per  square  inch. 

For  any  number  of  pounds  pressure  the  ratio  is  obtained  in 

the  same  way,  viz.,  say  for  75  pounds  gauge  pressure,  i-  =    -^1/ 

P        14.7 

=  6.1   as  given    in  column    3,   Table    XVII.     The    hyperbolic 

logarithm    of    6.1     =  1.8083X2,116.8  =  3,827.8    foot-pounds. 

Then  •-"   "^'      =.  i  16  of  a  horse  power,  theoretical,  to  compress 
33>ooo 

one  cubic  foot  of  air  per  minute  to  73  pounds  gauge  pressure; 
to  which  must  be  added  the  friction  of  the  compressor. 

The  foot-pound  work  isothermally  per  pound  of  air  is  ob- 
tained by  multiplying  the  foot-pounds  for  one  cubic  foot  by  the 
number  of  cubic  feet  in  a  pound  at  atmospheric  temperature ; 
thus  at  62°  in  Table  XV.,  13.141  cubic  feet  =  i  pound,  and 
13. 141  X  3,827.8=  50,301  foot-pounds. 

Analyzing  the  isometrical  card,  Fig.  49,  for  the  work  due  to 
compression  only,  and  the  work  due  to  delivery  as  shown  on  the 
diagram ;  we  find  the  whole  work  at  4  atmospheres  absolute  or 

44. 1  pounds  gauge  pressure  to  be  as  follows;   then  A  =  4  hyp, 

log.  =  1.3863  X  2,116.8  =  2.934.5  foot-pounds  per  cubic  foot, 
and  44.1  X  144  =  6,350.4  X  .25  stroke  =  1,587.6  foot-pounds 
in  delivering  i  cubic  foot  of  free  air  when  compressed  iso- 
thermally to  44. 1  pounds  per  square  inch  gauge  pressure.  Then 
2,934.5  —  1,587.6=  1,346.9  foot-pounds  expended  in  compres- 
sion only,  for  i  cubic  foot  of  free  air  at  44. 1  pounds  gauge 
pressure. 

Adiabatic  compression  reaches  a  much  higher  theoretical 
work  value,  while  the  actual  work  of  compression  has  an  inter- 


ACTUAL    WORK    OF    THE    COMPRESSOR. 


169 


i».__l ^l^.^.S' 


mediate  work  value  depending  upon  the  amount  of  heat  absorp- 
tion by  the  walls  of  the  compressor. 

In  Fig.  50  is  shown  the  theoretical  card  of  adiabatic  com- 
pression for  4  atmospheres  absolute,  44.  i  pounds  gauge  press- 
ure, and  in  the  shaded  part  the  comparative  work  due  to  the 
curve  of  compression  only,  while  the  work  of  delivery  is  repre- 
sented in  the  unhatched  rectangle. 

The  formula  for  the  work  of  compression  for  the  complete 
stroke  of  a  compressor  is  derived  from  the  difference  in  temper- 
ature multiplied  by  the  mechan- 
ical equivalent  of  air  at  constant 
pressure,  Mcp  =  184.7.  Then 
T,  -  T  X  184.7  =  W,  the  work. 
The  difference  in  temperature 
may  be  obtained  by  the  differ- 
ence of  absolute  temperatures 
in  column  2,  Table  XVI.,  and 
the    mechanical    equivalent  for 

air  is    derived   from   the  Joule  equivalent   multiplied    by 
specific  heat  of  air;   778  X  .2375  =  184.7. 

In  the  case  of  the  diagram  Fig.  50,  the  work  of  compression 
of  one  pound  of  air  from  60°  F.  temperature  to  4  atmospheres 
absolute  or  44.  i  pounds  per  square  inch  gauge  pressure  will  be 
T,  —  T,  or  t  —  T  as  in  column  2,  Table  XVI.,  or  by  the  formula 
used  for  that  column  as  before  stated.  The  absolute  temper- 
ature, 779  —  52  I  =  258°  X  184.7  =  47,652.6  foot-pounds  per 
pound  of  free  air.  Then  for  the  work  per  cubic  foot  of  free  air 
at  60°  F.  divide  the  number  of  foot-pounds  per  pound  by  the 
number  of  cubic  feet  of  free  air  in  Table  XV.  at  60°  per  pound 


Fig.  50.— adiabatic  card. 


the 


of  air.     Then 


47,652.6  _ 


3,637  foot  pounds  and 


3.63; 


=  , 1 102 


13-1  "  33.000 

of  a  horse  power  per  cubic  foot,  to  which  must  be  added  the 
proportional  friction  of  the  compressor.  The  work  of  compres- 
sion due  to  delivery  and  to  the  compression  curve  separately  is 
of  interest.     The  point  of  stroke  of  the  piston   at  which  the 


I  70  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

pressure  is  reached  may  be  taken  from  column  4,  Table  XVII., 

for  gauge  pressure,  or  may  be  computed  by  the  ratio  of  the  ab- 

p'"         V 
solute  pressures  from  the  formula,  log.  ^-      =  — '  and 


P  V  log.  index 

.00 

=  the  point  of  stroke.      As,  for  example,  ■'— ^  =  4,  the  ratio  for 

14.7 

the  absolute  pressures. 

The   common    log.    for  4  is  0.60206  X  .711  =0.42806,   the 

log.   index  of  which  is  2.68,  and ^  =  -373.     the     point     of 

stroke  from  the  terminal  when  full  pressure  is  reached. 

The  whole  number  of  foot-pounds  when  divided  by  the  vol- 
ume of  one  pound  of  air  in  cubic  feet,  for  the  temperature  of 
the  free  air  taken  into  the  compressor,  equals  the  foot-pounds 

per  cubic  foot.     Then  "^^'    ^'"     =  3,637.6  foot-pounds  per  cubic 

I3-I 

foot  of  free  air  at  60°  F.  compressed  to  4  atmospheres  or  44.  i 

gauge  pressure ;  and  as  the  mean  pressure  for  44.  i  is  28.9  pounds 

per  square  inch,  and  the  point  of  stroke  for  the  full  stroke  is 

.373  from  the  terminal,  then  44.1  X  .373  =  16.45,  which  is  the 

proportion  of  the  mean  pressure  due  to  delivery. 

280 
Then  — '—  =  1.756,  the  ratio  of  the  foot-pounds  due  to  de- 
16.45 

livery,  to  the  total  foot-pounds  per  pounds  of  air.      Then  -^'    -^ 

1.756 

=  2,071  foot-pounds  for  the  delivery,  and  3,637  —  2,071  =  i  ,566 

foot-pounds  due  to  the  adiabatic  compression  curve  of  the  card. 

This  method  can  be  applied  to  the  actual  work  of  the  com- 
pressor by  using  the  relative  pressures  in  columns  2,3,  and  4 
in  Table  XVIII.,  which  are  based  on  actual  conditions  of  a  com- 
pressor in  which  four-tenths  of  the  heat  of  compression  is  ab- 
sorbed during  compression. 

Table  XIX.  has  been  computed  by  the  formula  and  examples 
on  page  167  of  the  work  of  isothermal  compression  for  column  2 
for  pressures  of  every  5  pounds  as  in  column  i.  Column  3  has 
been  computed  by  the  formula  and  examples  on  page  169  of  the 


ACTUAL    WORK    OF    THE    COMPRESSOR. 


171 


work  of  adiabatic  compression,  and  column  4  represents  the 
actual  foot-pound  work  of  compression  pet  cubic  foot  of  free  air 
in  compressors  that  absorb  four-tenths  of  the  heat  due  to  com- 
pression, and  has  been  obtained  from  six-tenths  of  the  differ- 
ence of  columns  2  and  3  added  to  the  isothermal  foot-pound 
work  in  column  2. 


TABLE  XIX. — Foot-Pounds  of  Work  Required  for  Compressing  Air. 
Theoretical  for  Columns  2  and  3,  and  for  the  Actual  Conditions 
with  Partial  Cooling  in  Column  4  as  Found  in  Tari.e  XVIIL  For 
One-Stage  Compression. 


Foot- 

Foot- 

Foot- 

Foot- 

Foot- 

Foot- 

Pressure 

pounds 

pounds 

pounds 

Pressure 

pounds 

pounds 

pounds 

in 

per  cubic 

per  cubic 

per  cubic 

in 

per  cubic 

per  cubic 

per  cubic 

pounds. 

foot. 

foot, 

foot, 

pounds. 

foot, 

foot. 

foot, 

isothermal. 

adiabatic. 

actual. 

isothermal. 

adiabatic. 

actual. 

I 

2 

3 

4 

I 

2 

3 

4 

5 

619.6 

649.5 

637-5 

55 

3.393-7 

4,188.9 

3,870.8 

10 

1,098.2 

1, 192.0 

1. 154-6 

63 

3,440.4 

4,422.8 

4,029.8 

15 

1.488.3 

i,66r.2 

1,592-0 

65 

3.577-6 

4,645.4 

4.218.2 

20 

I. 817.7 

2,074.0 

1,971-4 

70 

3,706.3 

4.859-6 

4,398.1 

25 

2,  102.6 

2,451-6 

2,312.0 

75 

3,828.0 

5.063.9 

4.569-5 

3^ 

2,353-6 

2,794.0 

2,617.8 

80 

3.942.9 

5.259-7 

4.732.9 

35 

2,578.0 

3,  iir.o 

2,897.8 

85 

4.051-5 

5.450.0 

4.89  .6 

40 

2,780.8 

3.405-5 

3.155-6 

go 

4.155-7 

5.633-1 

5.042.1 

45 

2,966.0 

3.681.7 

3.395-4 

95 

4.254-3 

5.8  9-3 

5.187.3 

50 

3, 136.2 

3.942.3 

3,619.8 

100 

4,348.1 

5,981-2 

5.327-9 

Other  equations  or  formulas  may  be  used  for  obtaining  the 
foot-pounds  of  work  required  to  compress  air  to  any  desired 
pressure.     For  example,  the  adiabatic  volume 

V        the  adiabatic  vol.  .  .  ^  V  "=   ^   t 


and 


V  initial  vol.  v 

Then  the  ratio  of  the  absolute  volumes  raised  to  the  power  of 
.406  logarithmically  is  equal  to  the  ratio  of  the  temperatures 

due    to    the    equivalent    compression;    also    —  =    (i 

■p^   "" 
P. 

ure  is  derived  from    the    volumes    and  the  temperature  from 

the  relative  pressures. 

V  •"'        t 
Then    for  working  the  equation  —      =    -  we  may  use  the 

Table  XVII.;  in  column   2  we  find  the  adiabatic  ratio  of    14.7 


(i)      =   _  are   also  logarithmic  ratios  from  which  the  press- 


\;2  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

gauge  pressure  by  interpolation  to  be  1.64,  the  log.  of  which  is 
0.21484  X  .406  =  0.087225,  the  index  of  which  is  1.222,  which 
is  equal  to  the  ratio  of  the  absolute  temperatures  as  found  in 

column  2,  Table  XVT.,  or  ^^  =   1.2222°. 

522° 

Again  we  have  (  ^|       =  _  as  explained  before. 

For  the  work  of  compression  we  have 

W=l:4o6  ^  j^^/p-_    ^_ 
.406  Vp  / 

In   which    — —  =  3-438,  a  constant,     d  R  =  the  difference 
.406 

of  the  foot-pound  equivalents  of  specific  heat  at  constant  press- 
ure, Mcp  =  184.77,  and  the  specific  heat  at  constant  volume 
M  c  V  =  1 3 1. 6,  which  =  53-17.  and  T=  the  normal  absolute 
temperature  from  60°  F.  =  522°. 

For  example,  to  obtain  the  foot-pound  work  for  adiabatic  com- 
pression from  60°  F.  to  two  absolute  atmospheres,  or  14.7  pounds 
gauge  pressure,  we  have  as  per  equation  above  3.438  X  53.17  X 

522  X  f   ^        —  I  )  =  the  foot-pounds  for  one  pound  of  free  air, 
\14.7  / 

and  this  product  divided  by  13.  i  =  the  foot-pounds  of  work  per 

cubic  foot.     The  operation  will  then  be  for  the  last  term  of  the 

equation    ^     =  2,  the  logarithm  of  which  is  o.  30 1 03  X  . 29  =  log. 
14.7 

0.08729,  the  index  of  which  is  1.2225,  and    1.2225  —  i  =  .2225. 

The  total  product  will  then  be  21.231  foot-pounds  per  pound  of 

air,  and  "-  '"-^     =   1,620  foot-pounds  per  cubic  foot  of  free  air 
I3-I 

compressed  from  60°  F.  to  14.7  pounds  gauge  pressure.  This 
differs  slightly  in  amount  from  the  method  of  computation  by 
temperatures  on  account  of  not  carrying  out  fully  the  decimal 
system. 

The  saving  in  foot-pound  work  by  compressing  air  that  is 
moist  even  to  saturation  has  been  demonstrated,  by  experiments 


ACTUAL    WORK    OF    THE    COMPRESSOR.  1/3 

made  in  France  by  M.  Mallard,  to  be  5}^  per  cent  at  3  atmos- 
pheres, 7^  per  cent  at  4  atmospheres,  1 1  per  cent  at  5  atmos- 
pheres, and  12  per  cent  at  7  atmospheres.  This  should  be 
observed  as  an  advantage  in  foot-pound  work  by  compressing 
air  in  rainy  or  foggy  weather. 


Chapter  XII. 


MULTI-STAGE 
AIR   COMPRESSION 


MULTI-STAGE  AIR   COxVIPRESSION. 

The  great  range  of  pressures  through  which  compressed  air 
is  used,  calls  for  pressures  varying  from  i  pound  to  3,000  or  more 
pounds  per  square  inch ;  but  the  greatest  field  of  its  work  is 
found  between  50  and  100  pounds  gauge  pressure.  Even  at 
100  pounds  the  greatest  economy  of  production  is  found  in  the 
two-stage  effect,  which  eliminates  to  a  large  degree  the  heat- 
resisting  jDower  acquired  during  the  second  half  of  the  piston 
stroke  in  a  single-stage  compressor.  For  higher  pressures  the 
economy  of  two-stage  compression  is  largely  increased  up  to 
500  pounds,  and  with  three-stage  compression  up  to  1,000 
pounds,  and  with  four-stage  compression  up  to  3,000  pounds. 

The  great  heat  generated  by  single  compression  to  high 
pressures  is  apparent  by  referring  to  Table  XVI.,  where  it  will 
be  seen  that  the  single-compression  temperature  for  a  pressure 
of  200  pounds  reached  673°  F.,  which  is  above  the  melting- 
point  of  lead,  and  will  fire  woodwork.  The  effect  of  such 
great  heat  on  the  packing  and  lubricants  of  a  compressor  are 
apparent;  hence  the  necessity  for  a  two-stage  process  wath  in- 
tercooling  when  compressing  air  to  above  100  pounds  pressure. 
The  heat  of  single-stage  compression  is  graphically  shown  in 
the  diagram  Fig.  45,  where  the  temperatures  are  vshown  for  dif- 
ferent free  air  intakes  at  0°,  60°,  and  100°  F.,  and  the  heat  of 
compression  temperatures  at  the  pressures  of  atmospheres  up  to 
2  I  and  of  pounds  gauge  pressure  up  to  294.  Of  course  the  ab- 
sorption of  heat  by  the  cylinder  walls  modifies  the  temperature 
somewhat,  but  the  fire  pump  before  described  shows  that  press- 
ures from  air  at  the  ordinary  temperature  of  a  room  will  ignite 
combustibles  at  above  350  pounds  pressure. 

The  introduction  of  water  into  the  cylinder  as  formerly  prac- 


178  COMl'RESSKI)    AIR    AND    ITS    APPLICATIONS. 

tised  has  had  but  little  j)ractical  effect,  and  unless  introduced  in 
quantities  to  keep  down  the  temperature  does  not  add  to  heat 
economy,  and  in  lar^^'c  (juantities  adds  to  the  cost  of  work.  The 
manner  and  time  of  injection  greatly  affect  its  usefulness  in  cool- 
ing the  air,  so  that  if  drawn  in  by  the  suction  of  the  piston  its 
spraying  effect  is  lost  1)y  its  contact  with  the  cool  incoming  air, 
and  the  spray  can  only  wet  the  walls  and  piston  at  best.  If  it 
is  forced  in  as  a  fine  spray  at  the  moment  that  the  compression 
has  raised  the  temperature  enough  to  be  absorbed  by  the  water, 
say  through  the  last  half  of  the  stroke,  it  requires  power  and  the 
operation  of  a  pump,  at  a  cost  that  seriously  affects  the  economy 
of  the  water-injection  system.  Besides  the  entanglements  ap- 
pertaining to  this  method  of  obtaining  compressed  air  at  moder- 
ately high  pressures,  the  compressed  air  is  loaded  with  moisture 
which  is  not  all  dropped  in  the  receiver,  in  active  operations, 
but  is  carried  along  the  transmission  pipes  in  a  misty  or  satu- 
rated condition,  and  becomes  a  nuisance  in  the  exhaust  of  oper- 
ating machines.  The  uncertainty  of  the  quantity  of  water 
entering  a  cylinder  with  a  quick-working  piston  is  a  source  of 
danger  from  concussion,  and  finally  the  wear  and  tear  of  water- 
injection  cylinders  from  the  inability  to  obtain  pure  water  has 
been  one  of  the  principal  causes  of  the  abandonment  of  this 
class  of  compressors  by  experienced  builders. 

TWO-STAGE    COMPRESSION. 

The  practice  of  two-stage  compression  for  moderate  press- 
ures, say  to  100  pounds,  has  been  long  in  use  in  the  compressors 
of  the  Norwalk  Iron  Works,  with  a  fair  claim  for  economy  over 
the  increased  friction  from  the  second  cylinder.  For  pressures 
above  too  pounds  further  compounding  becomes  necessary,  as  a 
matter  of  both  economy  and  safety.  Safety  being  in  some  cases 
an  important  element  in  eliminating  as  far  as  possible  the  lia- 
bility of  explosive  eff'ect  from  high  temperature  and  its  effect 
upon  the  oil  of  lubrication,  this  will  be  discussed  further  on. 

In  Fig.    5  I  is  shown  an   outline  card  of  two-stage  compres- 


MULTI-STAGE    AIR    COMPRESSION. 


>;9 


sion  to  75  pounds  in  which  the  maximum  pressure  of  over  80 
pounds  was  reached  in  order  freely  to  deliver  the  air  through 
exit  valves  of  restricted  area.  The  depressed  inlet  curve  of  the 
second-stage  card  shows  one  of  the  losses  in  multiple  compres- 
sion, which  is  due  to  the  small  area  of  the  intercooler,  its  con- 
nections, valves,  and  to  the  shrinkage  of  volume  by  the  inter- 
cooler, which,  if  its  capacity  is  not  equal  to  isothermal  cooling, 
causes  a  loss  in  the  work  of  the  second  cylinder.  With  cooling 
receivers  of  large  capacity  the  continuous  working  value  of  the 
second  cylinder  rises  to  its  proper  function,  and  the  inlet  card 


1 

m 

s^^ 

^ 

1 

1 

/ 

/ 

i 

/ 

/ 

---- 

_____ 

n 

A 

/" 

y 

■^ 

K  ' 

/ 

At 

mospf 

eric  1 

ine 

/ 

. 

J 

Absolute  Z 

ro.Pi 

easur 

lU 
10 


Fig.  51.— two-stage  card. 

lines  come  more  near  to  the  delivery  line  of  the  first-stage 
cylinder.  The  possibilities  of  economy  may  then  rise  from  4 
per  cent  to  about  i  5  per  cent  of  the  work  lost  by  heat  in  two- 
stage  compression,  above  the  isothermal  work. 

The  heat  loss  by  one-stage  compression  to  80  pounds  from 

60°  F.  is  equal  to  5 » -  5  9  ~  3 '  94-  _  ^^^  p^j.  ^gj^^.  of  the  foot-pound 

3.942 
work  of  isothermal  compression,  theoretical;  the  figure  being 
from  the  adiabatic  and  isothermal  columns  in  Table  XIX.  The 
actual  loss  may  be  much  less  in  the  most  efficient  water-jacketed 
head  compressors,  as  shown  in  a  comparison  of  columns  2  and  4 
in  Table  XIX.     Taking  the  figures  for  80  pounds  from  these 

columns  we  have  "^'^^ ~  3 '94-  „    _tq^  pg^.  qq^x^  Jqss  in  foot- 

3.942 
pounds  of  the  work  of  isothermal  compression. 


i8o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


The  following  table  will  serve  to  illustrate  the  large  saving 
that  it  is  possible  to  effect  by  compounding.  This  table  gives 
the  percentage  of  work  lost  by  the  heat  of  compression,  taking 
isothermal  compression,  or  compression  without  heat,  as  a  base. 


TABLE    XX. — Power  Lost  by  One,   Two,  and  Four  Stage  Compression. 


Gauge 
pressures. 


Per  cent. 
6 :) 30.00 


8j. 

I03. 
20J. 
4OJ. 
600. 

Soo. 


One 
stage. 


34.00 
38.00 

52.35 
68.63 

83.75 
90.00 


Two 
stage. 


Per  cent. 
13-38 
15.12 
17.10 
23.20 
29.70 
32.65 
35.80 


Four 
stage. 


Per  cent 

4.65 

5- 04 

S.oo 

9.01 

12.40 

15.06 

16.74 


Gauge 

pressures. 


1,000 
1,200 
1 .  400 
1,600 
1.800 
2,000 


One 
stage. 


Per  cent 

96.  S  J 

106.15 

IgS.oo 

IIO.OO 

116.80 
121.70 


Two 
stage. 


Per  cent 
37.00 
40.00 
41. 6d 
42.90 
44.40 
44.60 


Four 
stage. 


Per  cent. 
1 6.  go 

1745 
17.70 
18.40 
19.12 
20.00 


In  columns  2,3,  and  4  no  account  is  taken  of  jacket  cooling, 
it  being  a  well-known  fact  among  pneumatic  engineers  that 
water  jackets,  especially  cylinder  jackets,  though  useful  and 
perhaps  indispensable,  are  not  efficient  in  cooling,  especially  so 
in  large  compressors.  The  volume  of  air  is  so  great  in  propor- 
tion to  the  surface  exposed,  and  the  time  of  compression  so 
short,  that  little  or  no  cooling  takes  place.  Jacketed  heads  are 
useful  auxiliaries  in  cooling,  but  it  has  become  an  accepted 
theory  among  engineers  that  compounding  or  stage  compres- 
sion is  more  fertile  as  a  means  of  economy  than  any  other  sys- 
tem that  has  yet  been  devised.  The  two  and  four  stage  figures 
in  this  table  (columns  3  and  4),  are  based  on  reduction  to  atmos- 
pheric temperature  60°  F.  between  stages.  This  is  an  impor- 
tant condition,  and  in  order  to  effect  it  much  depends  on  the 
intercooler.  In  this  device  we  have  a  case  of  jacket  cooling 
which  in  practice  has  been  found  to  be  efficient  where  engineers 
specify  intercoolers  of  proper  design.  While  cooling  between 
stages  we  may  split  the  air  up  into  thin  la3'ers  and  thus  cool  it 
efficiently  in  a  short  time,  a  condition  not  possible  during  com- 
pression. This  splitting-up  process  should  be  done  thoroughly, 
and  while  it  adds  to  the  cost  of  the  plant  to  provide  efficient 
coolers,  it  pays  in  the  end. 


iMULTI-STAGE   AIR    COiMPRESSION.  l8l 

Referring  again  to  the  table,  we  learn  that  when  air  is  com- 
pressed to  lOO  pounds  pressure  per  square  inch  in  a  single-stage 
compressor  without  cooling,  the  heat  loss  ma}-  be  thirty-eight 
per  cent.  This  condition,  of  course,  does  not  exist  in  practice, 
except  perhaps  at  exceedingly  high  speeds,  as  there  will  be 
some  absorption  of  heat  by  the  exposed  parts  of  the  machine. 
It  is  safe,  however,  to  say  that  in  large  air  compressors  that 
compress  in  a  single  stage  up  to  lOO  pounds  gauge  pressure, 
the  heat  loss  is  thirty  per  cent.  This,  as  shown  in  the  table, 
may  be  cut  down  more  than  one-half  b}'  compounding  or  com- 
pressing in  two  stages,  and  with  three  stages  this  loss  is 
brought  down  to  eight  per  cent  theoretically,  and  perhaps  to 
three  or  five  per  cent  in  practice.  As  higher  pressures  are 
used,  the  gain  by  compounding  is  greater. 

The  practical  effect  of  compounding,  however,  does  not  re- 
sult in  any  material  economy,  unless  the  air  is  thoroughly 
cooled  between  the  stages.  Hot  air  in  the  cylinder  of  an  air 
compressor  means  a  reduction  in  the  efficiency  of  the  machine, 
because  there  is  not  sufficient  time  during  the  stroke  to  cool 
thoroughly  by  any  available  means.  Water  jacketing,  the  gener- 
ally accepted  practice,  does  not  effect  thorough  cooling.  The 
air  in  the  cylinder  is  so  large  in  volume  that  but  a  fraction  of 
its  surface  is  brought  in  contact  with  the  jacketed  parts.  Air 
is  a  bad  conductor  of  heat  and  takes  time  to  change  its  temper- 
ature. The  piston,  while  pushing  the  air  toward  the  head, 
rapidly  drives  it  away  from  the  jacketed  surfaces,  so  that  little 
or  no  cooling  takes  place.  This  is  especially  true  of  large 
cylinders,  where  the  economy  effected  by  water  jackets  is  con- 
siderably less  than  in  small  cylinders.  Leaks  through  the 
valves  or  past  the  piston  will  explain  many  indicator  cards, 
and  until  something  better  than  a  water  jacket  is  devised  it  is 
well  to  seek  economy  in  air  compression  through  compounding. 

In  the  case  of  high  pressures,  that  is,  from  500  to  3,000 
pounds,  it  is  essential  to  resort  to  compounding  on  the  most 
economic  lines  by  water-jacketing  to  the  furthest  extent  and 


l82 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


to  intercooling  to  a  possible  normal  temperature,  and  for  from 
2,000  to  3,000  pounds  the  four-stage  operation  becomes  imper- 
ative. 


Water  outlet 


Air 
outlet' 


THE    INTERCOOLER    IN    STAGE    COMPRESSION. 

One  of  the  most  important  adjuncts  in  the  economy  of  com- 
pressing air  by  stages  to  any  desired  pressure  is  the  intercooler. 
For  its  best  or  most  economical  effect  upon  the  work  of  a 
compound  or  multi-stage  compressor,  it  should  cool  the  passing 

air  between  each  of  the  compres- 
sion stages  to  its  normal  tempera- 
ture, and,  if  colder  water  is  avail- 
able, to  a  temperature  as  much  as 
possible  below  the  normal  temper- 
ature. We  illustrate  in  Fig.  52 
one  of  the  most  approved  combin- 
ations of  intercooler  and  receiver, 
the  Sergeant  type,  in  which  the 
heated  air,  direct  from  the  com- 
pressor, passes  into  an  upper 
opening,  and  down  between  a  large 
number  of  small  tinned  copper 
tubes,  held  vertically  in  a  sort  of 
chimney.  The  air  finally  emerges 
into  the  shell  portion  of  the  inter- 
cooler and  is  free  to  travel  through 
the  top  to  the  outlet  tube.  The 
smaller  tubes  mentioned  terminate 
at  either  end  in  plates,  into  which  they  are  expanded.  The 
cooling  water  enters  through  the  lower  pipe  and  is  forced  up- 
ward through  the  cooler  tubes,  and  finally  emerges  at  the  water 
outlet  at  the  top.  The  water  tubes  are  set  so  close  together  that 
they  divide  the  incoming  stream  of  air  into  thin  sheets  and  bring 
it  into  very  intimate  contact  with  the  cooling  surface.  As  stated, 
the  air  is  caused  to  enter  at  the  top  and  pass  downward,  while 


Fig.  52. -the  sergeant  intercooler. 


MULTI-STAGE    AIR    COMPRESSION.  1 83 

the  cooling  water  enters  at  the  bottom  and  passes  upward. 
This  is  the  accumulating  principle  upon  which  all  successful 
liquid-air  apparatus  have  been  constructed. 

A  properly  designed  intercooler  should  reduce  the  temper- 
ature of  the  compressed  air  to  its  original  point;  that  is,  to  the 
temperature  of  the  intake  air.  It  can  do  even  more  than  this, 
especially  in  winter,  when  the  water  used  in  the  intercooler  is 
of  low  temperature.  A  simple  coil  of  pipe  submerged  in  water 
is  not  an  effective  intercooler,  because  the  air  passes  through 
the  coil  too  rapidly  to  be  cooled  in  the  core,  and  such  inter- 
coolers  do  not  sufficiently  split  up  the  air  to  enable  it  to  be 
cooled  rapidly.  This  splitting  up  of  air  is  an  important  point. 
A  nest  of  tubes  carrying  water  and  arranged  as  described,  so 
that  the  air  is  forced  between  and  around  the  tubes,  is  an  im- 
portant point  in  an  efficient  form  of  intercooler.  If  the  tubes 
are  close  enough  together  and  are  kept  cold,  the  air  must  split 
up  into  thin  sheets  while  passing  through.  Such  devices  are 
naturally  expensive ;  but  first  cost  is  a  small  item  when  com- 
pared with  the  efficiency  of  the  compressor,  measured  in  the 
coal  and  water  consumed. 

Receiver-intercoolers  are  more  efficient  than  those  of  the 
common  type,  because  the  air  is  given  more  time  to  pass 
through  the  cooling  stages,  and  because  of  the  freedom  from 
wire-drawing  in  the  intake  of  the  next  cylinder,  which  may  take 
place  in  intercoolers  of  small- volumetric  capacit}'. 

See  Fig.  54  for  illustration  of  intercooler  of  the  Rand  Drill 
Co.,  and  further  on  for  that  of  the  Norwalk  Compressor. 

AFTERCOOI.ERS. 

Aftercoolers  are  in  some  installations  as  important  as  in- 
tercoolers. An  aftercooler  serves  to  reduce  the  temperature  of 
the  air  after  the  final  compression.  In  doing  this  it  serves  as  a 
dryer,  reducing  the  temperature  of  air  to  the  dew-point,  thus 
abstracting  moisture  before  the  air  is  started  on  its  journe}'. 
In  cold  weather,  with  air  pipes  laid  over  the  ground,  an  after- 


i84 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


X     ° 


MULTI-STAGE    AIR    COMPRESSION. 


185 


cooler  may  prevent  accumulation  of  frost  in  the  interior  walls  of 
the  pipes,  for  where  the  hot  compressed  air  is  allowed  to  cool 
gradually,  the  walls  of  the  pipe  in  cold  weather  act  like  a  sur- 
face condenser,  and  moisture  may  be  deposited  on  the  inside  for 
the  same  reason  that  we  have  frost  on  the  inner  side  of  a  win- 
dow pane.  In  using  these  aftercoolers,  and  also  intercoolers, 
it  is  good  practice  to  allow  from  8  to   10  cubic  feet  of  free  air 


Fig.  54.— the  rand  intercoolek. 

per  minute  for  each  square  foot  of  cooling  surface.  Further, 
an  allowance  of  i  pound  of  water  for  each  2  cubic  feet  of  free 
air  should  be  made. 

In  Fig.  53  we  illustrate  the  IngersoU-Sergeant  steam  actu- 
ated "  straight-line  "  compound  air  compressor  with  an  inter- 
cooler  attached  directly  to  the  top  of  the  cylinders.  The  inter- 
cooling  cylinder  or  drum  contains  a  water-circulating  coil  of  pipes 
around  which  the  air  passes  from  the  low  to  the  high  pressure 
cylinder.     The  pipe  surface  being  so  large,  the  air  is  cooled  to 


1 86 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


its  normal  temperature  or  possibly  below  when  cold  water  is 
available.  ' 

In  Fig.  54  is  illustrated  the  intercooler  of  the  Rand  Drill 
Company,  which  by  its  form  and  position  allows  of  a  very  large 
amount  of  cooling  surface  to  be  utilized  in  the  transfer  of  air 
from  the  low  to  the  high  pressure  cylinder  with  a  minimum 
amount  of  retardation  by  friction,  thus  giving  to  a  two-stage 
system  of  compression  a  high  efficiency. 

One  of  the  principal  advantages  of  two-stage  compression 
over  single-stage  compression  is  found  in  the  reduction  of  loss 
due  to  the  heat  of  compression,  and  this  represents  a  saving  in 
power,  since  the  resistance  due  to  compression  is  directly  pro- 
portional to  changes  in  temperature.     Other  reductions  in  losses 

are  found  in  reduction  of 
clearance  and  strains  and 
in  a  more  uniform  air  resist- 


lliijli  Pressure  Air  CijUnder 
Scale  liOO 


Iiitenucdiate  Air  Cylinder 
Scale  SUT 


ance. 

THREE-STAGE    AIR    COMPRES- 
SION. 

The  three  cards.  Fig.  55, 
represent  in  reduced  scale 
the  low-pressure,  interme- 
diate, and  high-pressure 
cards  of  a  three-stage  com- 
pressor for  compressing  air 
to  2,000  pounds  gauge  press- 
ure for  a  pneumatic  gun  bat- 
tery at  Fort  Winfield  Scott, 
vSan  Francisco,  Cal.  The 
discharge  from  the  low-pressure  cylinder  was  at  75  pounds, 
intermediate  at  375  pounds,  and  the  high-pressure  at  2,000 
pounds.  The  temperatures  of  the  incoming  air  were  brought 
down  to  slightly  below  normal  bv  efficient  intercoolers — the 
normal  temperature  being  75°  F.,  the  intermediate  inlet  show- 


Low  Pressure  Air  Cylinder 
Scale  iu 


-THREE-STAGE   AIR   COMPRESSION. 


MULTI-STAGE    AIR    COMI'RESSIUX, 


.87 


ing  73°  F.,  and  the  high-pressure  inlet  69°  F.  The  large  area 
of  the  receivers  seems  to  have  been  a  source  of  economy,  as 
shown  in  the  inlet  lines  of  the  cards.  The  cylinders,  being  all 
thoroughly  water- jacketed,  gave  the  following  temperatures  in 
the  discharge  pipe:  Low  pressure  320°  F.,  inter- 
mediate 289°  F.,  high  pressure  358°  F.,  the  adia- 
batic  differences  being  100°,  264°,  and  522°  respec- 
tively. This  is  a  most  interesting  showing  of  the 
value  of  proper  intercooling. 

The  combined  card  equivalent  to  the  three  cards 
Fig.  55  is  shown  in  Fig.  56,  in  which  the  cubic  feet 
per  revolution  is  scaled  at  the  bottom  of  the  card 
and  the  pressure  for  each  stage  is  shown  at  the 
right  of  the  vertical  leg.  The  delivery  lines  of 
these  cards  show  a  faultless  arrangement  of  air  con- 
nections and  valve  areas. 

FOUR-STAGE    AIR    COMPRESSION. 

In  Fig.  57  we  present  a  combined  air  card  of 
foiir-stage  compression  to  2,500  pounds  per  square 


Cubic  Feel  of  Air  pur  Revolution 

Fig.  56.— three-stage  compression  card. 


inch.  It  represents  the  conditions  derived  from  the  actual 
cards  taken  from  a  four-cylinder  single-acting  compressor  of  the 
Ingersoll-Sergeant  Drill  Company,  operated  by  two  non-con- 
densing Corliss  engines;  the  individual  steam  cards  of  which, 
with  the  air  cards,  are  shown  in  Fig.  58.  The  steam  cylinders 
were  18  by  36  inches,  direct  connected. 

The  low  and  first  intermediate  air  pistons  were  connected  to 
one  engine,  the  second  intermediate  and  high-pressure  air  pis- 
tons to  the  other  engine ;  the  engines  being  connected  on  one 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


shaft  with  cranks  at  right  angles.  The  four  single-acting  air 
cylinders  were  211^:^,  9,  7,  and  33L  inches  diameter  respectively, 
by  36-inch  stroke. 

All  the  air  cylinders  were  water-jacketed  and  provided  with 
intercoolers  of  the  Ingersoll-Sergeant  type.  The  first  inter- 
cooler  has  a  capacity  of  9  cubic  feet  as  against  7.241  cubic  feet 
in  the  low-pressure  cylinder,  with  a  cooling  surface  112  square 
feet.  The  second  intercooler  was  1.8  cubic 
feet  as  against  1.32  cubic  feet  in  the  first  in- 
termediate, with  60  square  feet  of  cooling 
surface.  The  third  intercooler  was  .7  cubic 
foot  as  against  .57  cubic  foot  in  the  second 
intermediate  air  cylinder,  with  35  square 
feet  of  cooling  surface ;  while  the  after- 
cooler  was  of  1.6  cubic  feet  capacity  with  45 
square  feet  of  cooling  surface.  The  uniform 
lines  of  air  intake,  as  shown  on  the  separate 
cards,  are  of  interest  and  are  due  to  the 
large  intercooler  capacity  in  its  relation  to 
the  following  cylinder.  For  this  relation  we 
find  that  the  first  intercooler  had  6.8  times 
the  volume  of  the  second  compressing  cyl- 


Ctttiic  Feet 


Fig.  57— four-stage  air  compression  card. 


multi-sta(;e  air  compression. 


189 


inder,  and  the  second  intercooler  had  3.2  times  the  volume 
of  the  following  or  third  compressing  cylinder,  while  the  third 
intercooler  had  a  volume  of  3.9  times  that  of  the  high-pressure 
cylinder. 

The  compressor  engines  made  58  revolutions  per  minute, 
compressing  419  cubic  feet  of  free  air  from  atmospheric  press- 
ure at  75°  F.  to  2,500  pounds  pressure,  and  delivering  the  air 


Imw  Pressure  Air 


High  Pressure  Air 


First  Intermediate  Air 


Fig.  58.— separate  air  cards  axd  steam  cards 

from  the  high-pressure  cylinder  at  230°  F.,  and  from  the  after- 
cooler  at  normal  temperature. 

The  horse  power  developed  at  the  maximum  air  pressure 
w^as  204  I.  H.  P.  in  the  engines  and  168.5  in  the  compressor, 
showing  an  efficiency  of  .826  for  the  friction  losses  in  the 
entire  plant.  The  temperature  of  the  air  throughout  the 
stages  is  of  interest,  and  from  the  record,  the  air  entered  the 
first  stage  at  74°  F.,  was  delivered  at  176°,  entered  the  second 
cylinder  at  90°,  was  delivered  at  142°,  and  finally  delivered 
from  the  high-pressure  cylinder  at  230°  F.  The  figures  also 
show  that  2  cubic  feet  or  possibly  more  free  air  can  be  com- 
pressed to  2,500  pounds  per  square  inch  per  indicated  horse 
power.  We  have  no  test  for  general  efficiency  under  full  work- 
ing pressure  of  this  four-stage  compressor;  but  tests  made 
while  running  from    135  to  170  atmospheres  gave  an  efficiency 


igo  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

of  about  65  per  cent,  and  from  the  work  of  filling  the  receivers 
from  I  to  171  atmospheres,  an  average  efficiency  of  68  per  cent; 
so  that  in  regular  work  at  full  load  the  efficiency  may  be  antici- 
pated to  average  about  63  per  cent. 

In  tests  made  by  representatives  from  the  Cornell  Uni- 
versity, the  several  efficiencies  of  the  apparatus  are  given  as 
follows:  Mechanical  efficiency,  90.4  per  cent;  efficiency  of  com- 
pression, 88.9  per  cent;  volumetric  efficiency,  89.34  per  cent. 
The  product  of  these  is  71.8  per  cent,  a  considerabl}'  higher  fig- 
ure than  either  of  those  obtained  from  calculations  ba.sed  on  the 
receiver  pressure.  We  are  unable  to  account  for  the  difference 
except  on  the  supposition  that  the  indicated  work  of  the  air 
cvlinders  was  not  accurately  measured.  All  indicator  cards  are 
liable  to  certain  percentages  of  error,  and  there  is  an  unusually 
large  probabilit}^  of  error  in  the  measurement  of  the  indicated 
work  in  the  second  intermediate  and  the  high-pressure  air 
cylinders,  since  the  pistons  of  the  indicators  used  in  taking  the 
cards  were  only  of  i(  and  0.1  inch  diameter,  respectively;  and 
the  nominal  scale  of  the  springs  was,  respectively,  250  and 
1,250  pounds  to  the  inch. 

The  method  of  computing  the  efficiency  of  the  apparatus  by 
comparing  directly  the  work  done  in  the  steam  cylinders  with 
the  work  of  storing  the  air  in  the  receiver,  measured  by  the 
volume  of  the  receiver  and  the  difference  between  the  pressure 
at  the  beginning  and  end  of  the  test,  eliminates  the  errors  of 
measuring  the  work  done  in  the  air  cylinders  by  means  of  indi- 
cator diagrams.  By  this  m.ethod  it  is  not  at  all  necessary  to 
take  diagrams  from  the  air  cylinders,  although  such  diagrams 
are  valuable  for  determining  approximately  the  proportions  of 
work  done  in  the  several  cylinders,  the  value  of  the  water 
jackets  and  intercoolers  in  reducing  the  total  work  of  com- 
pression, the  mechanical  efficiency  of  the  apparatus,  and  the 
so-called  efficiency  of  compression,  or  the  ratio  of  the  indicated 
work  in  the  air  cylinders  to  the  theoretical  work  of  isothermal 
compression. 


MULTI-STAGE    AIR    COMPRESSION.  I9I 

It  is  fair  to  state  that  the  efficiency  obtained  above  is  based 
on  tests  made  when  the  plant  was  newly  set  up  and  running 
under  conditions  in  some  respects  less  favorable  than  those 
which  may  obtain  when  it  has  been  longer  in  service.  Con- 
sidering this  fact  and  the  very  high  pressure  to  which  the  air  is 
raised,  the  figures  of  efficiency  above  attained  appear  very 
creditable  to  the  designers  and  builders  of  this  remarkable 
compressor. 

THE     FOOT-POUND      WORK     OF     MULTIPLE-STAGE     AIR 
COMPRESSION. 


Using  the  following  formulas,  we  have  for  the  first  stage, 

y     (v 

y  -  I  VP 


W=P„V^^(PV--i)  (,.) 


and  for  the  second  stage, 

when  the  air  is  cooled  to  normal  temperature  between  the 
stages,  and  for  computation,  P,  =  2,116.8,  the  pressure  of  the 
free  atmosphere  per  square    foot.       V  =  i    cubic  foot  or  any 

number    of    cubic   feet.      — ^ —  =  ~ —  =  3-438.        -   =   the 

y  —   I  .406  P 

logarithmic  ratio  of  the  normal  and  the  assumed  absolute  pres- 

r  •  y  —  I  -406  J 

sure  or  compression. =  — - —  =  .29.     —  i  and  —  2  are 

y  1 . 406 

the   integers   of  the   index  of  the  logarithmic  product  of  the 

pressure  ratio  and  its  exponent. 

For  a  two-stage  compression  to  100  pounds  gauge  pressure 
and  to  50  pounds  for  the  first  stage,  the  computation  is  as  fol- 
lows : 

First  stage,  2,116.8  X   i   X  3.438  =  7,277.55, 


p   _  64.7 


P        14.7 

4.401  the  ratio;  the  logarithm  of  which  is  0.64355  i  X  by  the  ex- 
ponent .29  =  o.  186629,  the  index  of  which  =  1.537  —  1  =  .537» 
which  X  7,277.55  =  3,908  foot-pounds  per  cubic  foot.     To  this 


192 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


vShould  be  added  the  compressor  friction  and  deducted  the  value 
in  foot-pounds  of  the  cooling  effect  of  the  cylinder. 

For  the  second  stage  we  have  2, 1 16.8  X  i  X  3-438  =  7,277.55 
as  before  and  the  index  of  the  first  compression  logarithm  1.537, 
to  which  must  be  added  the  index  of  the  log.  of  the  ratio  of  the 

second  stage,  which  is  "-  ■—  — zlZ  =   1.7727  =  log.  0.24861  X 

P,  64.7 

.29=  0.072097,  the  index  of  which   is    1.181,  to  which   add  the 

index  of  the  first  stage    1.537  =  2.718,  and  2.718  —  2  =  .718  X 

7'277.55  =  5,228  foot-pounds  per  cubic  foot,  and  .158  of  a  horse 

power  per  cubic  foot,  to  which  should  be  added  the  compressor 

friction,  say  5   per  cent,  and  deduct  for  cylinder  cooling,  say  8 

per  cent,  which  will  be  about  3  per  cent  to  be  deducted;  or  the 

theoretical  work  will  nearly  cover  the  losses  and  gains. 

TABLE    XXI. — Horse-Power    Developed    to    Compress    100    Cubic    Feet    of 
Free   Air.   from  Atmosphere   to  Various  Pressures. 


Gauge  pressure, 
pounds. 

One-stage 

compression 

D.  H.  P. 

Gauge  pressure, 
pounds. 

Two-Stage 

compression 

I).  H.  P. 

Four-stage 

compression 

\).  H.  P. 

10 

3.60 
5-03 
6.28 
7.42 

?.47 

9.42 
10.30 
II. 14 
11.90 
12.07 
13-41 

14.72       ! 
15.94 
17.06 
18.15 

6o.. 

11.70 

10  80 

15 

80 

TO    cn 

2  ) 

15.40                         14.20 
21.20            1             18.75 
o±  en                        OT  Rn 

25 

200..  .  . 

30 

300. .  .  . 

35 

400. .  .  . 

27.70 

29-75 
31.70 
33.50 
34.90 
36-30 
37.80 
39.70 
43.00 
45-50 

24.00 
25.93 
27.50 

28. 90 

40 

500 

45 

600 

700 

50 ' 

55 

8  00.. 

6j 

QOO. . 

31  00 

70 

1 ,  000. ...            

31. So 
33.30 
35.65 
37.80 
39.C6 
40.15 

80 

1,20  ) 

90 

1,600.. 

100 

2,000 

2,300 

3,000 

For  a  three-stage  compression  to,  say,  1,000  pounds  gauge 
pressure,  we  have  from  the  value  of  the  first  three  terms  as  be- 
fore 7,277.55  X  by  the  sum  of  the  indices  foi  the  logarithms  of 
the  ratios  for  each  previous  stage  -\-  the  index  of  the  last  stage 
—  3,  the  integers  for  three  stages.  The  third  stage  will  be 
p,  _   1,014.7  _ 


114. 7 


8,846    log.    0.946747  X  .29  =  0.274556,    index 


MULTI-STAGE   AIR    COMPRESSION.  1 93 

1. 8815  +2.718  =  4-5995  -  3  =  1-5995  X  7,277. SS  =  ii,640foot- 
pounds  per  cubic  foot,  or  .352  of  a  horse  power  per  cubic  foot. 

The  compression  of  100  cubic  feet  of  free  air  per  minute  and 
the  work  developed  in  horse  power  has  been  tabulated  from  the 
formulas  before  given  for  one,  two,  and  four  stage  compression. 
It  represents  very  nearly  the  actual  work  of  compression  in  first- 
class  compressors,  allowing  for  cylinder  cooling,  intercooling, 
and  friction,  which  last  partially  neutralizes  the  cylinder-cooling 
effect.     Table  XXI. 

The  economy  in  power  saved  by  two-stage  compression  for 
even  as  low  a  pressure  as  60  pounds  is  very  evident  by  inspec- 
tion of  this  table,  which  shows  for  sixty  pounds  a  saving  of  14.5 
per  cent  and  for  100  pounds  17.8  per  cent.  The  saving  for 
1,000  pounds  pressure  of  a  four-stage  compression  over  a  two- 
stage  is  18,8  per  cent. 
13 


Chapter  XIII. 


THE  EXPANSION  OF 

COMPRESSED  AIR  AND  THE 

WORK  OF  THE   MOTOR 


THE    EXPANSION    OF   COMPRESSED   AIR    AND    THE 
WORK    OF    THE    MOTOR. 

The  expansion  of  compressed  air  does  work  in  a  cylinder  on 
the  same  lines  as  in  the  work  of  compression.  The  curve  of 
expansion  from  normal  temperature  for  compressed  air  is  adi- 
abatic  in  the  negative  sense,  for  by  compression  the  pressure 
and  work  are  cumulative,  while  by  expansion  they  are  depletive, 


100 

E 

00 

•g     no 

8      70 

\D 

\C 

J.      GO 

1      50 

s 

Usfful  Ifnrk    V 
//(  Mohjr 
(Coid  Air) 

^         \ 

1      ^« 

~B 

10 

R 

^    c 

)                         .2 

0 

5                       .7 

5 

% 

X)  G 

Volume  Cu.  Ft. 

Fig.  59.— expansion  card. 


as  shown  by  the  card  Fig.  59,  in  which  the  three  radial  lines  of  air 
pressure  and  work  are  shown.  The  curves  are  all  hyperbolic 
in  form,  and  for  expansion  are  subject  to  an  inversion  of  the 
equations  and  formulas  used  in  compression.  The  theoretical 
equations  for  the  expansion  of  air  when  no  heat  is  absorbed 
by  the  motor  cylinder  are  the  same  as  for  compression  with 
the  principal  terms  inverted.  Therefore  the  1.406  powers  of 
the  specific  volumes  are  inversely  proportional  to  the  corre- 
sponding absolute  pressures  and  temperatures. 


198  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

We  have  then  the  proportion  v  '""■'  :  v,  """  :  :  p,  :  p  and 
p  V  '•""■  =  p,  V,  '  ""■  V,  and  p,  being  the  greater  volume  and  press- 

ure ;   also  _       =   tl>.      Then  using  logarithms,   1.406  X  log.  — 
v'  p  _^^^  V, 

=  log.  ^  and  log.  -P  =  1.406  X  log.  —J,  or  P-  =  — ! 
p  p,  V  p,  V 

If  we  assume  the  initial  volume  v,  =  i,  and  the  original  ten- 
sion or  pressure  Pj  =  i  atmosphere,  we  have  for  the  pressure 
or  tension  p  when  the  air  has  expanded  to  twiee  its  volume,  or 

v  =  2  V,,  without  loss  of  heat  (adiabatic),  i  .406  X  log.  2  =  log.  -. 

P 
Then,  for  example,  1.406  X  log.  0.30103  =  log.  0.423248  =  log. 

1.      Then  log.  0.423248  index  =  2.65  and  —  =  =  .377  at- 

p  P         2.65 

mosphere. 

For  temperature  of  expansion  we  have, 

'"""  _  T,  _  absolute  reduced  temperature 

\v,/  T        absolute  normal  temperature 

Then  for  a  specific  volume  v,  expanded  to  2   volumes   from  a 

temperature  of   60°   F.  =  522°  absolute,    we   have    (- — M        — 

"^        ' ^  and  log.  2  =0.30103  X  0.406  =  log.  0.1222  18,  index 

462  -|-    t 

1.325  =  the  ratio  of  the  respective  temperatures.  Then  522  X 
1.325  =  691.6  —  522  =  169.6°.  the  drop  in  temperature  due  to 
the  expansion  of  one  volume  to  two  volumes  from  60°  F.  For 
the  terminal  pressure  from  the  adiabatic  expansion  of  com- 
pressed air  in  an  engine  or  motor  cylinder,  we  have  the  formula 

I  '■'""     —  P  =  terminal  pressure, 

R      -' 
in  which   p  is  the  absolute   initial   pressure  or  gauge  pressure 
plus     14.7,    and    P    the    absolute    atmospheric    pressure,     14.7. 

—  =  the  ratio  of  expansion  obtained  by  dividing  i  by  the  cut-off 
R 

expressed  in  tenths  of  the  stroke  of  the  piston.     Thus  for  a  cut- 
off of  A  or .  3,  ^  =3.333  the  ratio,  the  logarithm  of  which  must 
10  3 


THE    EXPANSION    OF   COMPRESSED   AIR.  1 99 

be  multiplied  by  the  exponent  1.406.  The  index  of  the  loga- 
rithmic product  becomes  a  divisor  of  the  absolute  initial  press- 
ure,  from  the  quotient  of  which  the  atmospheric  pressure  must 

be  deducted  for  the  terminal   pressure.      For  example,    for  — 

10 

cut-off  and  60  pounds  gauge  pressure,  we  have  —  =  3.333  log. 

3 

0.522835  X  1.406  =  0.735  106,  the  index  of  which  is  5.434;  then 

iAj_  =13.7—14.7=—!.  The  terminal  pressure  being  one 
5-434 

pound  less  than  atmospheric  pressure. 

By  a  series  of  terminal  pressures  computed  by  the  above 
formula,  a  card  may  be  made  indicating  the  terminal  pressures 
of  the  adiabatic  curve  for  any  number  of  divisions  so  arranged 
that  the  cut-off  may  represent  an  even  number  of  divisions,  and 
the  sum  of  all  the  divisions  divided  by  the  number  will  equal 
the  mean  pressure. 

As  an  example  we  illustrate  this  method  by  a  card   Fig.  60 

detailed  for  A  cut-off  at  100  pounds  gau^e  pressure. 
10 

The  approximate  mean  of  the  expansion  from  the  third  to 

the  fourth  division  will  be  as  follows :  The  ratio  of  expansion 

for  the   terminal    is  ^  =:  i  .333  log.  o.  12483  X   1.406  =  0.17551, 

•       1  o         rr^i  I  14-7  r       r  r        o  j    6 1  . 8   4-    1 OO 

mdex  1.498.    Then  — ^^  —  76.56  —  14.7  =  61.8  and  \ . 

1.498  2 

=  80.9  the  mean  pressure  due  to  the  expansion  of  the  fourth  space. 
The  next  terminal  will  be  A  =   1.666  log.  0.221675  X  1.406  = 

■-» 

0.311675,   index   2.05,   and — —    =55.9—14.7  =  41.2.      Then 

2.05 

^  •" L ^  =  51.5  the  mean  pressure  of  the  fifth  space,  and  so 

on  through   the  ten   spaces ;   the    whole  aggregating  -^"^'-^"^  = 

52.79,  the  mean  pressure  of  the  card  with  a  terminal  (^f  6.58 
pounds,    which   approximates    nearly   to    the   figures  given   as 


200  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

computed  from  the  ratios  in  the  3d  and  7th  columns  of  Table 
XXIII.  These  computations  and  the  values  given  in  Table 
XXIII.  are  theoretical,  and  take  no  account  of  the  clearance  in 
the  cylinder  and  ports  and  of  the  absorption  of  heat  by  the  air 
from  the  motor  cylinder.  It  is  noted  that  the  cylinder  of  a 
motor  is  much  colder  than  the  outer  air  when  compressed  air  at 
atmospheric  temperature  is  used,  and  heat  is  being  constantly 
absorbed  by  the  cylinder  and  given  to  the  expanding  air.  It 
will  be  readily  understood  that  the  walls  of  a  motor  cylinder, 

as  soon  as    normal   running  con- 

S27.9i 

ditions  are  established,  absorb  heat 
from  the  incoming  air  at  atmos- 
pheric temperature  until  a  moment 
after  the  cut-off,  when  the  con- 
dition becomes  reversed  and  the 
cold  expanding  air  receives  heat 
from  the  walls  of  the  cylinder  in 
an  increasing  degree  until  the  ex- 
haust  takes  place,  when,  if  under 

Fig.  60.— expansion  card.  ^  ' 

a  terminal  pressure,  the  tempera- 
ture of  the  contents  of  the  cylinder  suddenly  drops  to  the  point 
due  to  the  total  expansion  from  the  working  pressure  to  atmos- 
pheric pressure,  less  the  amount  of  heat  absorbed  at  full  press- 
ure or  given  to  the  expanding  air  during  the  expulsion  of  the 
cold  air  on  the  return  stroke  of  the  piston.  These  amounts 
are  small  in  their  effect  upon  motor  efficiency,  and  can  be  entirely 
eliminated  by  warming  the  motor  cylinder — just  the  opposite  of 
the  treatment  of  a  compressor  cylinder  for  increasing  its  effi- 
ciency. The  clearance  in  a  motor  cylinder  adds  to  its  mean 
pressure  at  the  expense  of  the  relative  volume  of  the  stroke  at 
the  cut-off.  The  volume  of  the  clearance  also  increases  the  vol- 
ume due  to  the  nominal  cut-off,  varying  with  the  cut-off  volume. 
In  the  following  table  is  given  the  actual  cut-off  due  to  the 
various  percentages  of  the  clearance  in  motor  cylinders  for  the 
nominal  cut-off  as  given  in  column  i . 


THE    EXPANSION    OF   COMPRESSED    AIR.  20I 

For  example,  let  the  cylinder  stroke  be  lo  and  the  clearance 
.07  per  cent,  cut-off   —,  then    10  X   .07  =  .7  -j-  10  =  10.7,  the 

actual  volume  of  cylinder  and  clearance.  Then  the  sum  of  the 
ratios  of  the  cut-off  and  clearance  divided  by  the  actual  vol- 
ume of  the  cylinder  and  clearance  equals  the  actual  clearance, 

3+  .7  =    -^  =  -3457  the    actual  clearance.     In  this    manner 
10.7 

the  following  table  of  nominal  cut-off  percentage  of  clearance 

and  actual  cut-off  has  been  computed.     The  rule  serves  for  any 

cut-off  and  clearance. 

TABLE   XXII.  — Excess  of  Cut-Off  Due  to  the  Percentage   of   Clearance 
FOR  the  Nominal  Cut-Off  in  Column  i,  for  Compressed-Air  Motors. 


Nominal  cut-oflf. 


Perci^ntage  of  Clearanci- 


.04 


.06 


o.  10 

.12 

.14 
.16 
.18 
.20 

.22 

.24 
.25 
.26 

.28 
•30 
.32 

•  34 

.36 

.38 

.40 
.42 

•  44 
.46 
.48 
.50 
.52 
.54 
.56 
.58 
.60 
.62 
.64 
.66 
.68 
.70 

•  72 

•  74 

•  75 


0.126 
.146 
.165 
.184 
.204 
.223 

•  243 
.262 
.272 
.281 
.301 
.320 
•340 
•359 
•378 
■398 
•417 
•437 
•456 
■475 
•495 
.514 

•534 
•554 

•  573 

•  593 
.612 
.632 
.651 
.670 
.690 
.709 
.729 
.748 

•  758 


0.135 
.154 

.174 
•193 
.212 
.231 

•  251 
.270 

•  279 
.289 

•  308 

•  327 
•346 
.366 

•  3S5 
.404 

•  423 
■  442 
.462 
.481 
.500 

•  519 

•  538 

•  558 

•  577 

•  596 
.615 

•  634 

•  654 
•673 
.692 

.711 

•  731 

•  750 
.760 


0.143 
.162 


.219 
.238 

•  257 
.276 
.286 

•  295 

•  314 
•333 

•  352 
•371 
•390 
.409 
•429 
•448 
.467 
.486 

•  505 

•  524 

•  543 
.562 
.581 
.600 
.619 
.638 

•  657 
.676 
.695 
•714 
■733 
•752 
.762 


0.151 
.170 
.189 
.207 
.226 

•245 
.264 
.283 

•293 
.302 
.321 
•340 
•359 
•378 
•396 

•  415 
•434 
.453 

■  472 
.490 

■  509 
.52S 

•  547 
.566 

.585 
.604 
.623 
.642 
.661 
.679 
.698 
•717 
.736 

•  755 
.764 


0.159 

•  177 
.196 

•  215 
•233 
.252 
.271 
.290 
.299 
.308 

■  327 
■346 
■364 

•  383 
.402 
.420 
•439 
•45S 
•477 
■495 

•  514 

•  533 

■  551 

•  570 

•  589 
.607 
.626 

•  645 
.664 
.682 
.701 
.720 

•  738 

•  757 
.766 


0.167 
.185 
.204 
.222 
.240 

•  259 
.277 
.296 

•  305 

•  315 
•333 
•352 
■370 
•389 
.407 

•425 
•444 
.462 
.481 
.500 
.518 

•  537 
•555 
•574 
•593 
.611 
.630 
.648 
.667 
.685 

•703 
.722 
•740 
•759 
.768 


.200 
.218 
.236 
•254 
•273 
.291 

•309 
.318 
•327 
•345 
•364 
.382 
.400 
.418 
•436 
•455 
•473 
.491 

•  509 

•  527 

•  546 
•564 
.582 
.600 
.618 
•637 

•  655 
•673 
.691 

.709 
.727 
■745 
■763 

•  772 


202 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Ill  Table  XXIII.  are  given  the  theoretical  conditions  in  re- 
gard to  the  pressures  and  temperatures  of  compressed  air  when 
expanding  in  the  cylinder  of  a  motor  engine,  to  which  correc- 
tions must  be  made  for  clearance  by  adding  the  additional 
amount  to  the  cut-off  as  per  Table  XXII.  for  various  percent- 
ages of  clearance,  for  a  definite  ratio  of  expansion,  from  which 
other  ratios  for  the  pressures  and  temperatures  may  be  com- 
puted from  the  formulas  given  for  each  column  in  Table  XXIII. 

TABLE  XXIII. — Ratios  of  Pressures  and   Temperatures  due  to  Expansion 
OF  Compressed  Air  in  a  Motor  Cylinder,  Theoretical. 


9 

3 

o 

0 
0 

ai 

oi  ft 

erf  X 

(0 

0 

cut-off. 

Ratio  of  mean 
to  total  absolute 

II 
.a, 
t\ 
S.2 

X 

CL, 

mean  pressure. 

Ratio  of 
mean  to  total 

[            aosoiuie 
pressure  during 
expansion  onlv. 
P  X  Ratio  -  P. 

Ratio  of 

initial  to  final 

temperature. 

T  X  R  =  T2  = 

absolute 

temperature  of 

exhaust. 

Ratio  of  initial 
to  final  absolute 

temperature 

due  to  cylinder 

expansion  only. 

T  XR  =  T,. 

Ratio  of 
initial  to  final 

absolute 

pressures  for 

ratio  of 

expansion. 

p  X  R  -  P  = 

final  pressure. 

I 

2 

3 

4 

5 

6 

7 

CIO 

in.  00      0. 

2493         0. 

1659 

0.39^8 

0.5131 

0.0391 

.12 

§■33 

29  3 

1935 

4210 

.5410 

.0505 

.14 

7-14 

3^93 

2201 

4484 

■  5657 

.0628 

.16 

6.25 

3665 

2458 

4735 

.5880 

.0758 

.iS 

5^55 

4020 

2708 

4968 

.6084 

.0894 

.20 

5. CO 

4360 

2950 

5186 

.6273 

.1037 

.22 

4-54 

4685 

3186 

5392 

.6448 

.1186 

•24 

4.16 

4996 

3416 

5586 

.6613 

.1341 

•25 

4.00 

5147 

3529 

5680 

.6692 

.1420 

.26 

3^84 

5295 

3641 

5772 

.6768 

.1501 

.28 

3^57 

5580 

3861 

5949 

.6915 

.1666 

■  30 

3^33 

5854 

4077 

6119 

•  7055 

.1836 

•32 

3.12 

6116 

4288 

62S2 

.7188 

.2010 

■34 

2.94 

6367 

4496 

6439 

•  7315 

.2189 

•36 

2.78 

6608 

47-0 

6591 

•  7438 

•2373 

•38 

2.63 

68  3  8 

4900 

6738 

•  7565 

.2561 

.40 

2.50 

7  58 

5097 

6881 

.7668 

.2752 

.42 

2.38 

7269 

5291 

7019 

•  7777 

.2948 

•  44 

2.27 

7470 

5481 

7154 

.7883 

■  3148 

.46 

2.17 

7662 

5670 

7285 

•7985 

■3351 

.48 

2.08 

7845 

5855 

7412 

.8084 

■  3558 

■50 

2.00 

8119 

6.38 

7537 

.8180 

.3768 

•  52 

1.92 

8185 

6218 

7658 

•8274 

.3982 

•54 

1.85 

8342 

6396 

7777 

.8365 

.4200 

•56 

1.78 

8492 

6572 

7893 

•  8453 

.4420 

•  58 

1.72 

8633 

6745 

8007 

.8540 

.4644 

.60 

1.667 

8767 

6919 

8119 

.8624 

.4871 

.62 

1. 61 

8893 

7  86 

8228 

.87-6 

.5101 

.64 

1.56 

9  )ii 

7254 

8335 

■  8787 

■5335 

.66 

I. 51 

0123 

7419 

8441 

.8866 

■5571 

.68 

'•47 

9227 

7583 

8544 

.8943 

.5810 

.70 

1.429 

9324 

7745 

8646 

.9018 

.6052 

•72 

1-39 

.9414 

79  6 

8746 

.9092 

.6297 

■74 

i^35 

•9497 

.8  64 

■  8844 

.9165 

•  6545 

•  75 

i^333 

•9536 

.8143 

■  8893 

.9200 

.6669 

THE    EXPANSION    OF    COMPRESSED    AIR.  203 

In  these  columns  R  is  the  ratio  as  in  column  2,  or  a  ratio  as- 
sumed by  the  addition  for  clearance  percentage  as  given  in 
Table  XXII.  Account  should  be  taken  of  the  heat  absorbed 
by  a  motor  cylinder  when  operated  by  compressed  air  at  atmos- 
pheric temperature.  When  air  is  reheated  before  entering  a 
motor  cylinder  so  as  to  exhaust  at  near  atmospheric  temper- 
ature, the  theoretical  conditions  will  not  be  materially  affected. 
The  formulas  from  which  Table  XXIII.  has  been  computed 
are : 


For  column  2, =  ratio  of  expansion. 

cut-off  ^ 

2.451    X 


For  column   s.  the  formula  is  ^ -U—  = 

^  R  R 


R 

ratio  of  mean  pressure  during  the  whole  stroke,  and  (p  X  ratio) 
—  P  =  mean  pressure.     The  first  terms  of  the  equation  as  shown 

below  become  '^-^   "^^    =  .2854,  adding  _  =  .3  =.  5854  the  ra- 
3-333  R 

tio  for  .3  cut-off  as  in  column  3. 

2.45.x  [.-(!)"■ 

For  column  4,  75 =  ratio  of  mean  to  total 

^  R  —  I 

absolute  pressure  during  expansion  only ;   for  which  the  value 

is  obtained  by  multiplying  the  absolute  initial  pressure  by  the 

ratio  and  subtracting  the  atmospheric  pressure,     p  X  ratio  — 

P  =  mean  pressure.     As  an  example,  for  computing  from  this 

formula,   we  assume  a  motor  running  with   50   pounds  gauge 

pressure  and  —  cut-off.       The   formula  may   then   be   written 


10 


1.451  X  fi  -  (-L-) 


jo3- 


3-33  -  I 
The    exponential    ratio    must    be    obtained    by   logarithms. 
Log.    3.333  =  0.522835  X  .408  =  log.   0.213316  index  of  which 

is    1.634  and   =  .6119  and  i  —  .61  ig  =  .3881   X  2.45  i  = 

1.634 


•95 


1233  I  and  '~ -^-^    =  -4077,  the  ratio  as  found  in  column  4. 


204  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

Column  5.    /—  )      the  ratio  being  for -A_ cut-off  3.333  as  be- 
VK./  10 

fore,  log.    X   by  the  exponent  gives   — ■ —  =  .6119,  as  found  in 

1.634 

column  5.  Then  if  a  motor  is  running  with  50  pounds  gauge 
pressure  and  at  60°  F.  atmospheric  temperature,  or  520°  abso- 
lute, and  (520  X  .61 19)  —  460  =  —  142"  F.  theoretical,  modified 
by  the  effect  of  the  clearance  and  heat  absorbed  from  the  outer 
atmosphere  through  the  cylinder.  In  this  case  the  final  press- 
ure at  exhaust  as  per  ratio  in  column  7  will  be  64.7  X  .  1836  = 

1 1.87  —  14.7  =— 2.83  pounds,  which  shows  that  a  —  cut-off  is 

10 

not  the  most  economical  point  unless  the  clearance  is  sufficient 
to  bring  the  final  pressure  to  the  atmospheric  line  or  enough 
above  to  compensate  for  engine  friction. 

Column  6.     |  —  I     is  the  ratio  of  temperature  for  initial  and 

final  pressures,  and  is  obtained  by  the  same  method  as  for 
column  5. 

Then  for  —  cut-off  as  above  (520°  X  .7055)  —  460°  =  —  93.2°; 
10 

the  temperature  when  the  pressure  reaches  the  atmospheric 
line. 


Column  7.     VR/      is  the  ratio  of  initial   and  final  absolute 


R 

pressures  for  the  given  ratio  of  volume     (— )       which  is  the 

logarithmic  ratio  as  in  column  5,  divided  by  the  ratio  in  column 
2,  and  gives  the  terminal  pressure  in  the  cylinder;  as,  for  ex- 
ample, for  50  pounds  gauge  pressure  and  —  cut-off    (64.7    X 

10 

.1836)  —  14.7  =  —  2.83  or  nearly  3  pounds  negative  pressure. 

Now,  for  example,  take  the  clearance  effect  into  consider- 
ation for  the  same  pressure  and  cut-off.  We  find  that  for  a 
clearance  of  5  per  cent  the  nominal  cut-off  will  be  advanced  to 


a  real    cut-off  of    .333    and  -777  =  3  the   ratio.      Then    V  3 

■333 


(j) 


THE    EXPANSION    OF   COMPRESSED    AIR. 


205 


log.  .4771-1  X  .408  =  0.194665,   index   of  which  is   1.565   and 

— ^  =  .639  and  '-^  =  .213,   the  ratio  of  the  absolute  initial 
1-565  3 

and    final    pressures.      Then    (64.7  X  .213)  —  14.7  =  —  i,    the 
terminal  pressure. 

Thus  we  find  that  at  60  pounds  gauge  pressure  —  cut-off 


10 

with  5  per  cent  clearance  will  give  a  terminal  pressure  of-|-  1.2 
pounds,  which  is  a  very  economical  point  of  cut-off  for  this 
pressure  and  clearance. 

TABLE  XXIV. — Mean  and  Terminal  Pressures  in  an  Air  Engine  or 
Motor.  Theoretical  and  Not  Including  Clearance.  With  Ratios  for 
Each  Cut-Off. 


0 

Pressures. 

Gauge  Prf.ssukes,  Pounds. 

Ratio. 

3 

CJ 

50- 

60. 

70. 

80. 

90. 

100. 

PXR-P. 

1%\ 

Mean 

Terminal  .  . 

13-5 
-  8.0 

17.8 
-  7.0 

22.2 
-6.0 

26.5 
-  4-9 

30.9 
-  3-9 

35-3 
-  2.8 

0.4360 
•1037 

i-j 

Mean 

Terminal  . . 

t8.6 
-   5-6 

23-7 
-  4-1 

28.9 
2.7 

34.0 
-  r-3 

39-2 

+  •1 

44-3 
1.6 

•5147 
.1420 

*\ 

Mean 

Terminal  .  . 

23.2 
-  2.6 

29.0 

-    I.O 

34-9 

+  .8 

40.7 
2.6 

46.6 
4-5 

52.4 
6.3 

•5854 
i      .1836 

3  5      ) 
T55  i 

Mean 

Terminal  .  . 

28.0 
0.0 

3I-0 
3-1 

34-7 

2-3 

41.2 
4.6 

47.8 
6.9 

54-5 
9.2 

61.0 
"•5 

.6608 
.2281 

t\] 

Mean 

Terminal  .  . 

38.0 

5.8 

45-1 
8.6 

52.1 

II. 4 

59-3 
14. 1 

66.3 
16.9 

.7058 
.2752 

J%\ 

Mean 

Terminal  . . 

37.2 
9.6 

42.0 
16.8 

45-2 
13-4 

53-2 
17.2 

61.2 
21.0 

69.2 
24.7 

77-3 
28.5 

.8019 

.3768 

B      1 

Mean 

Terminal  .  . 

50.8 

21.7 

59-5 
26.5 

68.3 
31-4 

77-1 
36.3 

85.9 
41.2 

.8767 
.4871 

The  values  in  the  above  table  are  derived  from  the  ratios  in 
Table  XXIII.  and  may  be  interpolated  by  using  ratios  in  that 
table,  or  the  formula  by  which  they  were  computed  for  any  re- 
quired cut-off,  to  which  the  extensions  for  any  percentage  of 
clearance  may  be  added  from  Table  XXII. 


206  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


THE    WORK    OF    EXPANSION. 

The  work  of  expansion  of  air  from  any  temperature  to  the 
zero  of  absolute  temperature  in  foot-pounds  has  an  intrinsic 
value  measured  by  the  mechanical  equivalent  of  air  at  constant 
volume,  Mcv,  =  778  X  .1689=  13  1.6  foot-pounds  per  unit  of 
heat.  Then  from  60°  F.  the  absolute  temperature  is  520°  F., 
and  520  X  131.6  =  68,432  foot-pounds. 

From  32°  F.  it  is  492°  X  131.6  =  64,747  foot-pounds. 

By  another  formula,  the  atmospheric  pressure  P„  multiplied 
by  the  volume  of  i  pound  of  air  in  cubic  feet  at  atmospheric  press- 
ure at  any  specific  temperature,  and  the  product  divided  by  the 

P  V 

ratio  of  the  specific  heats.  —  i ,  or  —^ — -"  for  the  above  temper- 

.406 

ature,    the    work    will    then    be    — '- ^=68,300  foot- 

.406 

pounds. 

In  Table  XV.  are  given  the  volumes  of  i  pound  of  air  at  vari- 
ous temperatures.  The  variation  in  the  values  of  the  specific 
heat  of  air  at  constant  pressure  and  at  constant  volume,  as- 
signed by  different  investigators,  is  the  cause  of  the  discrepancy 
in  the  results  from  the  formulas  of  different  authors ;  see  article 
on  specific  heat  and  Table  XIV. 

For  ascertaining  the  amount  of  foot-pound  work  of  com- 
pressed air,  expanding  to  atmospheric  pressure  from  any  initial 

3  T   P    r  /P\-~l 

pressure,    we   have   the  formula,  -^      — ^  M  ~  (^/^      ~  foot- 
pounds of  work  per  pound  of  air,  adiabatic  expansion. 

For  example,  one  pound  of  air  at  2  atmospheres  29.4  pounds 
absolute  pressure,  14.7  pounds  gauge  pressure,  at  60°  F.,  is 
computed  from  the  following  figured  terms : 

2,116.8   r    /i4.7\l-| 

s  X  520°  X pr  1  —  I  ^^-^  r 

^      ^  .0807  X  492°  L   V29.4/  J 

8^„i79    X    1-3./-!= — ^=.788 

2   1.2599 


THE    EXPANSION    OF   COMPRESSED    AIR.  20/ 

I  —  .788  =  .2  12  X  83,179  =  17,634  foot-pounds,  and  ^^'^^  = 
1,346  foot-pounds  per  cubic  foot. 

For  any  other  pressure,  say  50  pound-gauge  pressure.  The 
sum  of  the  first  three  terms  is  a  constant,  viz.,  83,189,  and  the 
fourth  term  will  be 

[■-(6^P*]---V:5=ri=--' 

and  I  —  .609  =  .391  X  83,189  =  32,526.9  foot-pounds  per 
pound  of  air  expanded  from  50  pounds  gauge  pressure  to  at- 
mospheric pressure.      Then  ^-^ — 1?  =  2,483   foot-pounds  per 

13. 1 

cubic  foot. 

The  ratios  of  pressures  and  volumes  from  adiabatic  com- 
pression and  expansion  may  be   obtained  from  the  following 

formulas,  — i  =  [  _  )       and  —  =  ( — ' )      in  which  P,  and  v,  are 
p        Vv,  /  V,        Vp/ 

the  greater  pressures  and  volumes.  Then,  for  example,  for  the 
relative  volume  of  compression,  say  for  two  atmospheres  abso- 
lute   or    any   number    of   pounds   absolute    pressure,   we    have 

P, 

p        \29.4. 

dex  of  which  is  1.636  and =  .617,  the  ratio  of  compression 

1.636 

and  expansion.     Then  assuming  i  pound  of  air  13.  i  c',  we  have 

13. 1  X  .617  =  8.08  cubic  feet,  the  volume  of  i  pound  after  adia- 

I  ^  I 
batic  compression  to  14.7  pounds  gauge  pressure,  and  -^-^  = 

21.2  cubic  feet,  the  volume  of  13.  i  cubic  feet  of  air  at  14.7 
pounds  gauge  pressure  when  completely  expanded  adiabatically 
from  14.7  pounds  gauge  pressure. 

The  formulas  for  the  work  of  expansion  vary  slightly  in 
their  results  as  given  by  different  authors.  Using  Professor 
Unwin's  formula  for  foot-pounds  of  work  (theoretical)  for  one 
pound  of  air,  we  have 

-;^Pv  [i  -  (1^)'^]  =  3-438  X  2,116.8  X    13. 1  =95.336 


=  {-^^\  =  (—)      log-  ~  ~  0-30103  X  .71  =  0.21373,   the  in- 


208  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

for  the  first  three  terms,  and  for  an  expansion  from  3  absolute 
atmospheres  44.1,  to  atmospheric  pressure  14.7, 

[' -  (si^T]  ""^ '° ''^"'■'■'^  [' ■"  (i)"]- 

Then  —log.  3  =  0.477121  X   .29  =  log.  0.138365,  the  index  of 
3 

which    is    1.375    and  =  .7272,   and   i  —  .7272  =  .2728  X 

1-375 

95,336  =  26,007  foot-pounds  for  the  work  of  one  pound  (13. i 
cubic  feet)  of  air  expanding  from  29.4  gauge  pressure  to  atmos- 
pheric pressure ;    not   including  friction   and    lost  work    from 

leakage. 

Another  formula  from  Church's  "Mechanics  of  Engineer- 
ing," for  the  foot-pounds  of  expansion  of  i  pound  of  free  air 
compressed  and  used  for  work  in  a  cylinder,  is': 

3  T " —      I  —  (  —  )2     ,  in  which  the  cube  root  of  the  press- 

^       .0807 1„  L  Vp  /   J 

ure  ratio  is  used  as  the  exponent.     Then  for  30  pounds  gauge 

P  T  A    7 

pressure  and  —  =  ~^^ ,  T  =  absolute  temperature  of  the  work- 
P        44-7 

ing  air,  say  60°  F.,  and  t„  the  absolute  temperature  of  32°  F. 

The  figures  will  then  be 

2,116.8        r  /i4.7\4-i 

3  X  520  X  —-^ ^      I  —  f-^^)^    . 

.0807  X  492°  L  144.7/    J 


The  product  of  the  first  three  terms  is  83,179  X     y   = 

3-04 

.6905,  and   I  —  .6905  =  .3095.     Then  83, 179  X  .3095  = 


1.448 

25,743  foot-pounds,  the  work  of  expansion  of  one  pound  of  free 

air  (13. 1  cubic  feet)  at  60°  F.  from  30  pounds  gauge  pressure  to 

atmospheric  pressure.     ~^'^^-^  =  1,965  foot-pounds   per   cubic 

13-1 
foot. 

In  computing  the  practical  work  of  expansion  in  a  cylinder, 

the  actual  ratio  of  expansion  is  not  due  to  the  nominal  ratio  of 

the  cut-off  to  the  stroke,  since  expansion  also  takes  place  in  the 

volume  of  the  clearance  by  the  amount  of  the  piston  clearance 


THE    EXPANSION    OF    COMPRESSED    AIR.  209 

and  port  area.  As  the  nominal  clearance  is  expressed  in  parts 
of  10,  the  percentage  of  the  clearance  is  also  expressed  in  parts 
of  10.  Then  the  cut-off  plus  the  clearance,  divided  by  the 
cylinder  volume  plus  the  clearance,  equals  the  actual  cut-off, 
as  per  Tables  XXII.  and  XXIII.  and  examples  in  their  expla- 
nation. 

14 


Chapter  XIV. 


TRANSMISSION  OF  POWER 
BY  COMPRESSED  AIR 


TRANSMISSION    OF    POWER    BY   COMPRESSED    AIR. 

The  use  of  compressed  air  for  power  purposes  at  a  distance 
from  the  compressing  plant  is  no  longer  a  mooted  subject  of 
discussion.  Successful  use  for  even  great  distances  has  be- 
come a  fact  in  practice,  and  its  economy  is  no  longer  in  doubt. 
More  than  twenty  years  ago  the  distribution  of  compressed  air 
for  power  rental  attracted  attention,  since  which  time  it  has  made 
rapid  strides  in  useful  installations  that  are  widespread ;  not 
only  for  public  service,  but  for  operating  machines  and  tools 
in  machine  shops,  factories,  and  our  great  constructive  works. 

For  mining  and  drifting  in  tunnel  work  the  transmission  of 
compressed  air  for  running  drills  and  pumps  has  been  long 
known  as  the  leading  method  and  the  only  safe  and  economical 
means  of  operating  machinery  underground  and  throughout  the 
drifts  and  galleries  to  the  deep  headings  of  the  modern  mining 
system. 

The  conveying  of  compressed  air  for  a  few  thousand  feet 
had  been  long  in  use,  and  its  convenience  and  economy  could 
not  be  gainsaid ;  but  when  transmission  for  miles  came  to  be 
considered,  the  question  of  loss  of  power  had  its  period  of  dis- 
cussion ;  now  the  doubts  raised  have  been  put  to  flight  by  the 
later  practice  and  its  accomplished  facts. 

The  continuous  compressed  air  line  of  ten  and  twenty  miles 
has  at  last  become  an  actuality,  owing  to  the  progress  of 
manufacture  of  large  pipe  lines  of  great  sustaining  power,  by 
which  air  at  high  pressure  may  be  conveyed  through  pipe  lines 
of  suitable  size  to  guarantee  small  loss  from  air  friction.  The 
apparent  loss  by  friction  may  be  slightly  compensated  by  ex- 
pansion of  the  volume  at  a  lower  delivery  pressure,  so  that 
what  it  loses  in  pressure  it  gains  in  value ;  yet  the  fall  in  press- 
ure in  long  pipe  lines  does  involve  a  loss  in  transmission,  as 


2  14  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

vshown  by  the  loss  of  efficiency  in  the  motor  due  to  loss  of  ini- 
tial pressure. 

As  compared  with  other  means  of  transmitting  power  for 
great  distances,  air  is  always  available  and  can  be  discharged 
from  motors  or  pumps  with  a  health-giving  property  in  mines 
or  in  factories;  it  has  peculiar  advantages  in  underground  work. 

The  success  in  the  distribution  of  compressed  air  for  power 
and  refrigeration  during  the  past  twenty  years  in  Paris,  France, 
and  later  in  England,  vSwitzerland,  and  Germany,  has  set  aside 
all  doubts  as  to  its  utility  and  economy.  For  its  work  in  a  great 
city,  it  has  no  equal,  as  shown  by  the  multiplicity  of  operations 
carried  on  in  Paris  by  the  compressed-air  system  as  lately  de- 
veloped there.  The  compressed-air  plant  has  now  been  in- 
creased to  24,000  horse  power,  having  main  pipe  and  distribut- 
ing lines  aggregating  140  miles  in  length,  of  which  about  100 
miles  are  used  for  power  purposes  alone,  and  40  miles  for  the 
operation  of  pneumatic  clocks.  From  the  power  mains  the 
smaller  distributing  mains  aggregate  20  miles  in  length,  and 
supply  955  power  consumers,  and  also  1,637  establishments 
in  which  compressed  air  is  used  for  the  operation  of  pneumatic 
clocks,  of  which  there  are  about  7,000.  Not  only  is  compressed 
air  used  for  small  factory  power  and  refrigeration,  but  it  has 
become  a  most  convenient  power  for  elevators,  for  there  are 
nearly  two  hundred  passenger  and  freight  elevators  used 
throughout  the  mercantile  district  in  which  the  air  pipes  are 
laid.  A  more  detailed  description  of  this  interesting  plant  will 
be  given  further  on. 

It  is  truly  strange,  in  view  of  the  successful  operation  of  a 
public  supply  of  compressed  air  in  Paris  and  other  parts  of 
Europe  for  the  past  twenty  years,  that  our  otherwise  enterpris- 
ing American  cities,  so  noted  for  internal  improvements,  are  still 
behind  the  age  in  the  distribution  of  air  power  from  central 
plants. 

As  to  the  loss  of  power  by  transmission  through  long  lines, 
the  tests  made  with  the   Paris  plant  have  furnished  us  with  the 


TRANSMISSION    OF    POWER    BY    COMPRESSED    AIR.  215 

best  practical  results.  The  average  velocity  in  the  mains  of 
the  Paris  system  for  a  length  of  main  equal  to  55,000  feet — 
about  10  miles — was  found  to  be  20  feet  per  second,  and  the 
loss  due  to  friction  was  1.65  pound  per  mile.  This  for  10 
miles  would  amount  to  16.4  pounds  loss  in  pressure,  or  about 
18  per  cent  from  an  initial  pressure  of  92  pounds.  This  leaves 
a  clean  working  pressure  of  75  pounds  at  the  end  of  the  line, 
with  higher  pressures  all  along  the  line  in  a  municipal  dis- 
tribution with  one  continuous  pipe  line.  In  the  system  of  dis- 
tribution as  arranged  in  the  Paris  and  Birmingham  air  plants, 
the  drop  in  air  pressure  throughout  the  lines  does  not  exceed  8 
pounds. 

In  the  planning  of  a  compressed-air  transmission  system, 
especially  for  public  service,  a  consideration  of  future  wants  in 
the  first  installation,  by  the  laying  of  much  larger-sized  pipes 
than  are  required  for  present  use,  becomes  a  source  of  immedi- 
ate economy  in  air-pressure  loss,  and  will  obviate  some  of  the 
troubles  and  losses  that  are  now  felt  in  the  Paris  plants,  which 
have  been  caused  by  the  increased  demand  for  air  power  when 
its  convenience  came  to  be  recognized  by  the  community.  To 
summarize,  air  is  in  practice  proving  to  be  a  fairly  cheap  and 
most  convenient  transmitter  of  power,  allowing  fine  subdivi- 
sion and  transportation  to  remote  points,  with  the  crowning  and 
unique  quality  of  suffering  no  appreciable  loss  when  held  in 
storage.  For  intermittent  service  it  is  of  great  value,  allowing 
widely  varying  speed  of  tools,  dispensing  with  long  lines  of 
shafting  and  belts,  giving  free  head-room,  and  increasing  the 
shop-light  as  well  as  lessening  the  first  cost  of  roof  frames  when 
they  have  not  to  carry  shafting.  The  pipes  require  no  coating; 
they  radiate  no  heat,  and  therefore  can  be  put  in  close  corners 
without  increasing  the  fire  risk ;  their  direction  is  readily 
changed  in  any  plane  without  risk  of  pocketing  or  water-ham- 
mer, and  leaky  joints  are  not  a  nuisance  or  risk.  In  no  case 
are  exhaust  pipes  required,  and  in  most,  if  not  all  cases,  the 
exhaust  adds  to  the  men's  comfort. 


2l6  COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


COMPRESSED    AIR    FLOWING    IN    PIPES. 

When  compressed  air  flows  along  a  pipe  tliere  is  necessarily 
a  fall  of  pressure  due  to  the  resistance  of  the  wall  surface  of  the 
pipe,  friction,  and  consequently  the  volume  and  velocity  of 
the  air  increase  along  the  length  of  the  pipe  in  the  direction  of 
the  motion .  Generally,  in  compressed-air  transmitting  systems, 
the  air  is  delivered  into  the  mains  at  a  temperature  above  that 
of  the  surrounding  air,  or  of  the  earth  in  underground  lines. 
The  excess  of  heat  is  soon  absorbed  by  the  surrounding  medium, 
and  in  long  lines  the  transmission  may  be  said  to  be  isothermal. 
The  loss  of  pressure  is  independent  of  any  changes  in 
temperature ;  it  is  directly  proportional  to  the  length  of  the 
pipe  line  and  to  the  square  of  the  velocity,  and  inversely  as  the 
diameter  of  the  pipe.  The  gain  in  free  air  delivery  by  loss  of 
pressure  is  nearly  as  the  square  root  of  the  loss  in  pressure. 
From  experiments  made  for  friction  in  the  long  lines  at  the 
Mont  Cenis  tunnel  it  was  found  that  the  frictional  loss  in  press- 

v'  1 
ure  was  0.0936        ,  in  which  v  was  the  velocity  in  feet  per  sec- 
ond, 1  the  length  of  pipe  in  feet,  and  d  the  diameter  of  the  pipe 
in  inches. 

Other  formulas  were  used  in  the  experiments  for  obtaining 
the  friction  in  long  pipes  in  the  Paris  system,  in  which  the 
velocity  became  a  term  in  the  equation,  together  with  a  coeffi- 
cient of  decreasing  value  with  the  increase  in  size  of  the  pipe. 

Thus  the  coefficient  c  was  assigned  to  vary  as  .0027  (  i  -\~  ~^—  ), 

\  10  d/ 

in  which  d  is  the  diameter  of  the  pipe  in  inches. 

Using  D'Arcy's  coefficients  for  the  actual  diameters  of 
wrought-iron  pipe,  we  have  the  discharge  in  cubic  feet  of  com- 
pressed air  per  minute  under  the  terminal  pressure  from  a  pipe 
of  any  diameter  and  length  with  various  initial  and   terminal 

pressures   from    the   following  equation :    D  =  c  4/  Q    X  p  —  p, 

w  X  length 


TRANSMISSION    OF    TOWER    BY    COMPRESSED    AIR. 


217 


in  which  d'  is  the  fifth  power  of  the  actual  diameter,  p  —  p^, 
the  difference  between  the  initial  and  final  pressures,  w  the 
density  of  the  compressed  air  at  the  initial  pressure  as  in  col- 
umn 3,  Table  XXVI.  ;  the  length  of  the  pipe  line  in  feet. 

In  Table  XXV.  are  given  the  nominal  diameter  of 
wrought-iron  pipe  of  standard  sizes,  the  actual  diameter,  the 
value  of  the  coefficient  c,  and  the  value  of  the  coefficient  multi- 
plied by  the  square  root  of  the  fifth  power  of  the  actual  diame- 
ter, c^d°,  which  will  facilitate  computation. 

In  Table  XXVI.,  column  3,  the  weight  of  a  cubic  foot  of 
compressed  air  is  given  for  the  pressures  in  column  i,  multi- 
plied by  the  ra.tio  in  column  2,  or  by  the  formula,  w  =  (.068  X 
P)  -f  I  X  .0761,  where  P  is  the  initial  gauge  pressure  in  pounds 
per  square  inch  at  the  receiver  or  entrance  to  the  transmission 
pipe. 

For  an}'  pressure  not  found  in  the  tables  the  above  formula 
may  be  used,  as,  for  example,  for  500  pounds  gauge  pressure 
.068  X  500  =  34  -f-  I  =  35  X  .0761  =  2.663,  the  weight  of  i  cubic 
foot  of  air  at  500  pounds  gauge  pressure.     This  may  also  be 

obtained  by  the  ratio  of  absolute  compression  X  .0761,  ■>  ^'^ 
=  35  X  .0761  =  2.663,  S'S  before. 


14.7 


TABLE  XX\  . — Of  Nominal  and  Actual  Dlameters  and  Areas  of  Stand- 
ard Wrought  Iron  Pipe.  Coefficients  and  ISIultipliers  for  c-y/d''  ^^^ 
Different-Sized  Pipes. 


.5  a3  <" 

c  a  o 
o  cS  c 


2 
3 

3'A 

4 

4'A 


<.ss 


1.048 

1.38 

1. 61 

2.067 

2.46 

3.026 

3-56 

4.026 
4-5 


0.8626 
1.49 
2.03 
3-356 

4.78 

7.388 

9-83 

12.73 

15-93 


45-3 
47.8 
50.3 
52.7 
54-4 
56.1 
56-9 
57.8 
58.1 


■> 


5 

I 

45-3 

5 

86.0 

6 

138.3 

7 

297. 

8 

537. 

9 

876. 

10 

1,304- 

12 

1,856. 

14 

2,492. 

16 

<:.2.H 


5-025 
6.C65 
7.023 
7.98 
8.937 
10.019 
12.00 
14-25 
16.4 


19.99 

28.888 
38.738 
50.04 
62.73 

78.839 
113.098 
159.485 
211.24 


58.4 
59-5 
60.1 
60.7 
61.2 
61.8 
62.1 
62.3 
62.6 


^ 


3,298.0 

5,273- 

7.817. 

10,988. 

14,872. 

19,480. 

30,926. 

45.690. 

64,102. 


2I.S 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


For  the  amount  of  free  air  corresponding  with  any  given 
pressure  multiply  the  gauge  pressure  by  the  ratio  in  column  2, 
Table  XXVI.,  or  the  volume  of  discharge  for  any  terminal  press- 


d^  X  P  -  P 


ure  as  found   by  the  formula  D  =  c  4/ 

w  X  1 

or  by  the  ratio  of  compression  as  above  explained 


-  X  column   2, 


TABLE   XXVI. — Gauge   Pressures    and  Corresponding  Weight   of   a  Cubic 
Foot  of  Compressed  Air  and  its  Square  Root. 


Ratio 

of 

volumes. 

w 

Gauge 

pressure. 

Ratio 

of 

volumes 

P. 

w 

Gauge 
pressure. 

weight  of      \/v 
one  cubic  foot     co 

weight, 
lumn 

weight  of 
one  cubic  foot 

\/ weight, 
column 

at  pressure, 

0. 

at  pressure. 

3 

P 

column  I. 

P 

column  I. 

I 

2 

3 

4 

I 

2 

3 

4 

0 

I. GO 

0.0761           0 

276 

55 

4-74 

0.3617 

0.6  DO 

5 

1-34 

1020 

319 

60 

5.08 

3866 

.622 

10 

1. 68 

1278 

358 

65 

5.42 

4125 

.642 

15 

2.02 

1537 

392 

70 

5.76 

4383 

.662 

20 

2.36 

1796 

424 

75 

6.10 

4642 

.6S1 

25 

2.70 

2055 

453 

80 

6.44 

4901 

.700 

30 

3-04 

2313 

481 

85 

6. 78 

5160 

.718 

35 

3.38 

2572 

507 

90 

7.12 

5418 

.736 

4'o 

3.72 

2831 

532 

95 

7.46 

5677 

•753 

45 

4.06 

3090 

55(5 

100 

7.80 

5936 

.770 

50 

4.40 

3348 

578 

As,  for  example,  what  amount  of  free  air  can  be  discharged 
through  a  4-inch  pipe  5,000  feet  long;  initial  pressure  100 
pounds,  terminal  pressure  75  pounds?  Then,  as  per  above 
formula  and  per  Table  XXV.,  column  5,  c  Vd"  =  1,856,  VP  —  P, 
=  V~2^  =  5  X  1)856  =  9,280,  and  from  column  4,  Table  XXVI., 
V  w  =.77  ,  V  5,000  feet  =  70.71  ;  then  70.71  X  .77  =  54-44-  and 

^tjl =i  170.4    cubic  feet   per  minute   at  75   pounds    pressure. 

54-44 

The  ratio  in  column  2,  Table  XXVI.,  is  6.10  for  75  pounds  and 
1 70.4  X  6. 10  =  1 ,039.4  cubic  feet  of  free  air. 

The  following  tables  of  free  air  delivery  for  various  initial 
pressures,  and  for  differential  pressure  losses  for  lengths  of  500 
feet  for  the  actual  diameter  of  pipes,  were  computed  by  Mr. 
William  Cox  for  Mr.  W.  L.  Saunders,  and  have  been  kindly 
loaned  the  author  for  this  work. 


TRANSMISSION    OF    POWER    BY    COMPRESSED    AIR.  219 

TABLES   OF    COMPRESvSED-AIR    TRANSMISSION. 

{Couipiited  by    William   Cox.^ 

With  a  Discharge  of  Equivalent  Free  Air  in  Cubic 
Feet  per  Minute  from  Pipes  of  Various  Diameters 
from  I  to  10  Inches,  Each  500  Feei  Long,  with 
Various  Reductions  of  the  Final  Pressure. 

From  these  tables,  approximate  quantities  and  loss  of  press- 
ure may  be  obtained  for  any  required  length  of  pipe  line. 

For  Example. — It  is  required  to  deliver  2,000  cubic  feet  of 
equivalent  free  air  at  the  end  of  a  pipe  line  150  feet  long,  the 
initial  pressure  being  60  pounds,  and  the  loss  of  pressure  not  to 
exceed  10  pounds.      What  diameter  of  pipe  must  be  used? 

TABLE   XXVII. — Air  Transmission.     Initial  Gauge  Pressure,   45  Pounds. 


Reduction  of  Final  Pkessure  in  soo 

Feet. 

Diamete 

rof 

pipe. 

I  pound. 

2  pounds. 

3  pounds. 

S  pounds. 

7  pounds. 

9  pounds. 

12  pounds. 

I  inch. 

14 

20 

24 

30 

34 

37 

40 

iX  iiic 

hes.            26 

36 

44 

54 

62 

68 

74 

i>^       ' 

43 

60 

72 

90 

102 

112 

121 

2           ' 

95 

132 

159 

198 

226 

247 

268 

■^Vz        ' 

172 

239 

287 

358 

409 

446 

484 

0            ' 

281 

390 

470 

585 

667 

728 

791 

3K       ' 

419 

583 

701 

S74 

997 

1,080 

1,180 

4 

595 

827 

995 

1,240 

1,410 

1.540 

1,670 

4K       ' 

806 

1,120 

1.340 

1,680 

1, 9 10 

2,090 

2,270 

5 

1,050 

1,470 

1,770 

2,200 

2,510 

2.740 

2,980 

6 

i,6go 

2,350 

2,820 

3.520 

4,020 

4.380 

4,760 

7 

2,500 

3.480 

4.190 

5.220 

5.950 

6,500 

7,060 

8 

3.520 

4,900 

5.890 

7.340 

8,370 

9,140 

9,930 

9 

4.770 

6.630 

7,970 

9.930 

11,300 

12,300 

13,400 

ID 

6,240 

8,680 

10,400 

13,0^0 

14,800 

16,100 

17,660 

By  table  of  60  pounds  initial  pressure  under  3  pounds  loss, 
and  opposite  5 -inch  diameter  of  pipe,  we  see  that  the  delivery 
would  be  2,000  cubic  feet,  so  that  for  a  pipe  line  1,500  feet  long 

'^       —  9  pounds.     We 


the  loss  of  pressure  would  be  about  3  x 


500 


say  "  about  "  9  pounds,  because  the  loss  is  not  exactly  propor- 
tional to  the  length,  but  nearly  so  when  the  basis  of  length  is 
500  feet. 


220  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

TABLE   XXVIII. — Air   Transmission.     Initial   Gau(;e  Pressure,  6o  Pounds. 


Ri'iDUCTioN  OF  Final  Prf.ssurr  in  500 

Feet. 

pipe. 

I  pound. 

2  pounds. 

3  pounds. 

5  pounds. 

7  pounds. 

9  pounds. 

12  pounds. 

I  inch 

1 6 

22 

27 

34 

39 

43 

48 

1]^  inches. 

29 

41 

49 

62 

72 

79 

87 

i>4       " 

48 

67 

81 

102 

"7 

129 

143 

2 

107 

149 

I  So 

226 

259 

286 

315 

2'^          " 

193 

269 

325 

408 

469 

516 

569 

3 

315 

440 

532 

667 

7.6 

844 

930 

3^       " 

471 

657 

794 

996 

1, 140 

1.260 

1,380 

4 

668 

932 

1, 120 

1,410 

1,620 

1,780 

1,970 

4^       " 

905 

1,260 

I,  520 

1,910 

2,  igo 

2,420 

2,660 

5 

1,180 

1,650 

2,000 

2,510 

2,S8o 

3,170 

3,500 

6 

1,890 

2,650 

3,200 

4,010 

4,610 

5,080 

5.590 

7 

2,810 

3^920 

4,740 

5.950 

6,840 

7.530 

8,290 

8 

3,960 

5,520 

6,670 

8,370 

9,620 

10, 500 

I I , 600 

9 

5.350 

7-470 

9,020 

1 1 , 300 

13,000 

14,300 

15,700 

ID 

7,010 

8,710 

ii.Soo 

14,800 

17,000 

18,700 

20,700 

TABLE    XXIX. —Air  Transmission.     Initial  Gauge  Pressure,   75  Pounds. 


Reduction  of  Fin.al  Pressure  in  500 

Feet. 

pipe. 

I  pound. 

2  pounds. 

3  pounds. 

5  pounds. 

7  pounds. 

9  pounds. 

12  pounds. 

I  inch 

18 

25 

30 

38 

44 

48 

54 

\%.  inches. 

32 

45 

55 

69 

80 

89 

98 

i>^       " 

53 

74 

90 

"3 

131 

145 

161 

2           " 

,    117 

164 

199 

251 

289 

320 

356 

2%       " 

212 

296 

359 

453 

523 

579 

643 

3 

346 

484 

587 

740 

855 

946 

1,050 

3%       " 

517 

723 

876 

1,100 

1,270 

1,410 

1,560 

4 

734 

1,020 

1,240 

1,560 

i,8ro 

2,000 

2,220 

4>^       " 

994 

1,390 

1,680 

2,120 

2,450 

2,710 

3,010 

5 

1,300 

1,820 

2,210 

2,780 

3,220 

3,560 

3,950 

6 

2,080 

2,gio 

3,530 

4,450 

5,140 

5,690 

6,320 

7 

3,09^ 

4,320 

5,230 

6,600 

7,630 

8,440 

9,370 

8 

4,350 

6,070 

7.360 

9,290 

10, 700 

11,800 

13,100 

9 

5,880 

8,220 

9,965 

12, 500 

14.500 

16,000 

17,800 

10 

7,710 

10, 700 

13,000 

16,400 

19,000 

21,000 

23,300 

Professor  Unwin  has  estimated  that  10,000  horse  power  can 
be  transmitted  at  an  initial  pressure  of  132  pounds  a  distance  of 
20  miles  in  a  30-inch  main  with  a  loss  of  pressure  of  only  12  per 
cent ;  and  that  the  motor  efficiency  at  this  distance  may  vary 
with  cold  air  from  40  to  50  per  cent  and  by  reheating  to  300°  F. 
from  59  to  71  per  cent.  The  air  velocity  for  these  estimates  is 
based  on  20  feet  per  second  for  best  effect.  The  larger  mains 
indicate  a  large  saving  in  power  for  compression  or  for  motor 
use,  and  indicate  financial  economy  in  the  long  run,  especially 


TRANSMISSION    OF    POWER    BY    COMPRESSED    AIR. 


!2I 


where  future  possibilities  may  require  additional  air  power. 
One  of  the  great  mistakes  heretofore  made  in  piping  mining 
and  other  air  systems  has  been  due  to  a  false  estimate  of  future 
wants  or  a  mistaken  judgment  of  the  loss  in  air  friction. 


TABLE   XXX. — Air  Transmission.     Initial  Gauge  Pressure,   90  Pounds. 


Reduction  of  Fi.n-al  Pressure  in  soo 

Feet. 

Diameter  of 

pipe. 

I  pound. 

2  pounds. 

3  pounds. 

5  pounds. 

7  pounds. 

9  pounds. 

12  pounds. 

I  inch 

19 

27 

33 

41 

48 

53 

63 

ij^  inches. 

35 

49 

59 

75 

87 

97 

109 

i>^       " 

57 

80 

97 

123 

143 

159 

178 

2           " 

127 

178 

215 

273 

316 

351 

394 

2K          " 

229 

321 

390 

493 

572 

635 

712 

3 

375 

525 

636 

806 

934 

1,030 

1. 160 

3%       " 

560 

784 

950 

1.200 

1,390 

1.550 

1.730 

4 

794 

I.IIO 

1,340 

1,700 

1,980 

2,190 

2.460 

A%       " 

1,070 

1.500 

1.820 

2.310 

2,680 

2,970 

3.330 

5 

1,410 

1.970 

2,390 

3.030 

3.510 

3.900 

4.370 

6 

2,250 

3,160 

3.830 

4.850 

5.620 

6,240 

6,990 

7 

3.340 

4,680 

5,680 

7,190 

8,340 

9,260 

10,300 

8 

4.700 

6,590 

7.990 

10, 100 

11,700 

13,000 

14.500 

9 

6,360 

8.930 

10,800 

13,600 

15,800 

17.600 

19,700 

10           " 

8,340 

11,600 

14, 100 

17,900 

20,700 

23,000 

25,800 

TABLE    XXXI. — Air  Transmission.     Initial  Gauge  Pressure,    105  Pounds. 


Reduction  of  Final  Pressure  in  soo 

Feet. 

Diameter  of 

pipe. 

I  pound. 

2  pounds. 

3  pounds. 

5  pounds. 

7  pounds. 

9  pounds. 

12  pounds. 

I  inch 

20 

29 

37 

44 

52 

58 

65 

i>4^  inches. 

37 

52 

68 

81 

94 

105 

118 

iK       " 

61 

86 

III 

133 

155 

172 

194 

2          " 

129 

190 

245 

294 

341 

380 

427 

2>^         " 

245 

344 

443 

531 

617 

687 

772 

3 

401 

562 

724 

867 

1,000 

1,120 

1,260 

3K       " 

599 

839 

1,080 

1,290 

1,500 

1,670 

1,880 

4 

850 

1,190 

1.530 

1,830 

2. 130 

2.370 

2,670 

AYz       " 

1. 150 

1,610 

2,070 

2,480 

2,890 

3.220 

3.610 

5 

1.510 

2,110 

2,720 

3.260 

3.790 

4.220 

4.750 

6 

2,410 

3.380 

4.350 

5.220 

6,070 

6,760 

7.590 

7 

3.580 

5.010 

6,460 

7.740 

8,990 

10,000 

11,200 

8 

5.030 

7.050 

9.080 

10. 800 

12,600 

14,000 

15,800 

9 

6,810 

9.540 

12,200 

14. 700 

17,100 

19,000 

21.400 

10 

8.920 

12,500 

16, 100 

19. 200 

22,400 

24, 900 

28,000 

Air  losses  in  transmission  in  pounds  per  square  inch  for  defi- 
nite volumes  through  assigned  pipe  sizes,  at  the  most-used 
pressure  in  mining  and  mechanical  operations,  viz.,  80  pounds 
pressure,  are  given  in  Table  XXXII. : 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


TABLE  XXXII. — Loss  ok  Pressikk  ihkough  Friction  of  Air  in  Ph'Ks, 
IN  Pounds  per  Square  Inch  kor  Every  too  Feet  Length  ok  Pipe 
(Initial  Gauge  Pressure  8o  Pounds  at  Receiver). 


s  -  0)  rt  C 

•_^    3   (U   r-  — 

Size  of  Pipe. 

Rqui 

vol 

of  fr 

disc 

per  tn 

i". 

iK"- 

iK". 

2". 

2%". 

3'- 

4"- 

5"- 

6'. 

7"- 

8". 

10". 

12". 

14". 

25 
50 

75 
100 
200 
300 
400 
500 

750 
1,000 
1,500 
2,000 
3,000 
4,000 
5.000 
6,000 
7.500 
10,000 

I.O< 
2  4 

3 

.12 

45 
1-7 

•4 

7 
3  0 

8 

3 
3 

•13 

SO 

1  20 

2  '5 

3  30 

2 

17 
38 
67 
10 

50 

5 

.1 
.2 
•4 
■9 
I  8 
4  0( 

5 
7 

3 
3 

I 

I 

3 

.06 
.  10 

.40 
00 
60 
70 

•03 
.07 
.12 
•30 
.50 
1.20 
2  00 

I 
I 
3 

012 

03 

05 

12 

20 

45 

80 

30 

9 

00 

I 
2 

013 
023 
052 

':95 
22 

60 
85 
40 

5 

I 

012 

027 

048 

'15 

20 

30 

43 

68 

25 

.o'7 
.036 
07 
.10 
•15 
.22 
.40 

.015 

.026 

.041 

06 

.09 

•'7 

.012 
.018 
.028 
.04 
07s 

Example. — An  air  compressor  furnishes  500  cubic  feet  of 
free  air  per  minute  at  a  pressure  of  80  pounds  per  square  inch 
in  the  receiver.  If  this  air  is  used  at  the  end  of  a  3-inch  pipe 
1,000  feet  long,  the  loss  due  to  friction  will  be  ioX.4  =  4 
pounds.  If  the  same  volume  of  air  were  supplied  by  the  same 
compressor  at  the  same  pressure  and  passed  through  a  5 -inch 
pipe,  1,000  feet  long,  the  loss  would  be  only  .03  X  10  =  3  —  10 
pounds;  thus  illustrating  the  importance  of  using  pipe  of  large 
diameter.  Strictly  speaking,  the  loss  of  pressure  is  not  directly 
proportional  to  the  length ;  however,  for  all  practical  purposes 
it  may  be  taken  as  such. 

The  foregoing  table  represents  the  loss  by  friction  in  the 
pipe.  There  is  a  further  slight  loss  due  to  the  friction  of  the  air 
with  itself  at  the  mouth  of  the  pipe  as  it  leaves  the  receiver. 

All  leaks  in  compressors  or  valves,  air  receivers,  or  pipe, 
should  be  strictly  guarded  against  for  the  sake  of  economy  in 
the  running  of  compressed  air  and  steam  apparatus.  Air  leaks 
are  fully  as  expensive  as  steam  leaks,  and  should  be  as  care- 
fully stopped.  Too  many  operators  think  that  an  air  leak  is  of 
but  little  consequence,  but  it  should  never  be  allowed,  save 
where  needed  for  actual  ventilation. 


Chapter  XV. 


COMPRESSED-AIR 

REHEATING  AND  ITS 

WORK 


COMPRESSED-AIR    REHEATING    AND    ITS    WORK. 


One  of  the  most  important  economies  in  the  use  of  com- 
pressed air  is  the  saving  obtained  by  the  increased  volume  due 
to  reheating.  The  first  efforts  made  in  this  line  were  probably 
suggested  by  the  tendency  of  rock  drills  to  become  so  frosted  in 
the  exhaust  as  to  interfere  with  their  best  work. 

Experiments  made  by  placing  a  wad  of  oily  waste  in  a  cham- 
bered fitting,  close  to  the  steam  chest  of  a  drill,  which  was 
found  to  burn  freely  fed  by  the 
passing  air,  led  to  trial  of  a  miner's 
lamp  in  a  small  chamber,  by  which 
arrangement  the  products  of  com- 
bustion were  added  to  the  compressed 
air  and,  passing  through  the  cylin- 
der, modified  in  a  great  measure  the 
intensity  of  the  frosty  exhaust. 

In  Fig.  6 1  this  simple  reheater  is 
illustrated  in  its  primitive  form.     The  experiment  clearly  de- 
monstrated the  possibility  of  utilizing  the  heat  and  products  of 
combustion  for  their  full  value. 

Another  experiment  in  the  same  line  is  shown  in  Fig.  62, 
in  which  an}^  easily  combustible  fuel  can  be  enclosed  in  a  cham- 
ber above  a  wire-gauze  partition  in  an  enlarged  fitting  close  to 
the  air  chest.  An  opening  in  the  fitting,  not  shown  in  the  cut, 
allows  of  igniting  the  combustible  in  contact  with  the  wire 
gauze,  when  the  combustion  is  kept  up  by  the  passing  air  and  is 
fed  by  gravity  from  above.  This  method  of  reheating  intensi- 
fies combustion  and  is  fairly  safe  in  mine  drilling  and  pumping. 

Another  form  of  internal  combustion  reheater,  patented  by 
"Edison,"  is  illustrated  in   Fig.  63.  and   consists  of  a  chamber 


Fig.  61.— simple  keheater. 


226 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


within  a  chamber,  between  which  the  air  flows  and  is  heated 
by  a  fire  within  the  internal  chamber.     A  by-pass  regulated  by 

a  valve  allows  enough  air  to 
pass  under  the  grate  to  feed 
the  fire.  A  jacketed  pipe 
leads  the  products  of  com- 
bustion from  the  top  of  the 
fire-chamber  to  the  follow- 
ing main  air  pipe,  also  regu- 
lated by  a  valve.  A  closure 
in  the  main  intake  air  pipe 
produces  a  differential  press- 
ure which  insures  circulation 
through  the  fire-chamber. 
A  hand-hole  plate  at  the 
top  fastened  by  a  yoke  and 
screw    allows    of    access   for 

feedinor  fuel,  and  a  full-sized 
Fig.  62.— rock-drill  keheater.  ^ 

head  and  yoke  at  the  bot- 
tom allow  of  thorough  cleaning.  In  ordinary  operation  the  fire 
can  be  fed  and  ashes  blown  out  without  interrupting  the  main 
flow  of  air,  by  operating  the  by-pass  valves. 

Reheaters  of  the  class  used  in  the  Popp  compressed-air  sys- 
tem in  Paris  are  made  with  pipe  coils  in  a  stove  for  small 
motors,  and  with  cast-iron  double-chambered  stoves  in  which 
the  products  of  combustion  are  carried  to  a  chimney  and  wasted. 
The  Sergeant  reheater  ^Fig.  64)  is  a 
double-chambered  stove  in  which  all  the 
compressed  air  passes  vertically  through 
the  space  between  the  fire-box  and  the 
outer  shell.  The  fire  is  fed  from  the 
top,  and  can  be  stoked  through  the  open 
grate  at  the  bottom. 

This  form  of  reheater   is   in   general 
use,  and  is  as  simple  and  easily  managed       fig.  63.-edison-  keheater. 


COMPRESSED-AIR    REHEATING    AND    ITS    WORK. 


227 


as  is  possible  under  most  of  the  conditions  available  for  econo- 
mizing the  use  of  compressed  air  in  motor  engines. 

From  tests  made  with  this  heater  it  has  been  found  capable 
of  heating  340  cubic  feet  of  free  air  per  minute  at  40  pounds 
pressure  to  360°  F.,  giving  a  gain  of  35  per  cent  in  the  meas- 


Fig.  64.— the  sergeant  keheater. 


Tired  amount  of  work  done  by  the  air  after  passing  through  the 
heater,  compared  with  the  same  volume  of  air  when  used  cold. 
A  heater  of  this  size  will  heat  less  air  to  a  higher  tempera- 
ture or  more  air  to  a  lower  temperature,  than  stated  above; 
but  if  it  should  be  required  to  heat  more  than  400  cubic  feet  of 
free  air  per  minute,  to  get  the  best  economy  it  is  advisable  to 
use  the  heaters  in  series,  allowing  about  400  cubic  feet  of  free 
air  per  minute  for  each  heater.     The  heater  should  be  placed 


228 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


as  near  as  possible  to  the  point  where  the  air  is  to  be  used,  and 
ths  outlet  pipe  should  be  as  short  as  possible  and  well  covered, 
so  that  the  air  will  retain  its  heat. 

Trials  have  been  made  in  reheating  compressed  air  by  in- 
jecting steam  into  the  air  pipe  near  the  motor,  by  passing  the 
air  through  a  steam  boiler,  and  in  the  ^^lekarski  and  other  com- 
pressed-air systems  by  passing  the  air  through  a  tank  charged 
with  water  at  a  high  temperature. 

Experiments  have  been  made  with  a  combination  of  steam 
with  compressed  air  with  an  economy  of  25  per  cent  in  air  vol- 
ume by  an  expenditure  of  lyi  pounds  of  coal  per  horse-power 


Fig.  65.— the  "sergeant." 
Reheating  the  air  for  rock-drilling  and  pumping  in  Jerome  Park  Reservoir. 


hour  for  the  steam  used,  and  was  found  to  be  equivalent  to  an 
additional  horse  power  for  each  pound  of  coal  burnt  in  the 
heater. 

In  consideration  of  the  unavailability  of  steam  except  in  a 
few  locations  where  steam  at  high  pressure  is  in  use  near  the 
location  of  compressed-air  engines,  the  heating  of  compressed 
air  by  steam  for  motors  is  of  little  or  no  practical  value.  Re- 
heating by  the  hot-water  system  as  used  on  railway  cars  has 
proved  very  economical. 

The  reheater  of  the  Rand  Drill  Company,  Xew  York  City, 
is  illustrated  in  Figs.  66  and  67,  and  has  a  furnace  lined  with 
fire-brick  and  an  ordinary  fire  and  ash-pit  door.  The  heating 
surfaces  are  composed  of  concentric  annular  spaces  of  gradually 


COMPRESSED-AIR    REHEATING   AND    ITS    WORK. 


229 


increasing  area,  keeping  the  velocity  of  the  expanding  air  con- 
stant. The  air  enters  at  the  side  of  an  annular  chamber  shown 
in  Fig.  (^T ,  passing  around  the  heater  and  upward  and  down- 


FlG.    66.— THE   RAND   KEHEATER. 


ward  and  then  upward  through  the  thin  annular  spaces,  making 
its  exit  at  the  top  of  the  interior  and  hottest  space. 

In  a  test  with  a  reheater  of  this  type  having  8;/  square  feet 
of  heating  surface,  530  cubic  feet  of  free  air  under  60  pounds 
pressure  were  heated  from  84°  to  376°  F.  in  one  minute;  with 
exhaust  air  from  the  motor,  as  a  forced  draft,  the  temperature 


'30 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


was  raised  to  450°  F.  for  the  same  quantity  of  air;  300°  is  the 
most  practicable  temperature  to  operate  motors  and  drills  on 
account  of  oil  lubrication ;  but  the  air  temperature  at  the  re- 
heater  may  be  higher  to  compensate  for  the  distance  of  trans- 
mission. 

The  use  of  superheated  water  forced  into  tanks  for  car  motor 
service  has  become  an   established   S3^stem,  showing  the  best 


Fig.  67. 

economy  for  this  class  of  service,  and  seems  to  be  the  only 
available  means  that  does  not  require  the  management  of  a  fire 
on  the  motor  car. 

The  hot-water  reheater  of  the  Mekarski  system  as  used  on 
a  number  of  compressed  railways  in  England,  France,  and 
Switzerland  is  illustrated  in  Fig.  68.  The  reheater  is  charged 
at  the  station  with  water  at  about  100  pounds  or  more  pressure 


COMPRESSED-AIR    REHEATING    AND    ITS    WORK. 


68.— MEKAKSKI      RE- 
HEATER. 


at  a  temperature  at  or  above  338°  F.,  containing  nearly  1,200 
heat  units  per  pound  of  water.  In  the  early  water  reheaters 
of  this  class  the  air  was  injected  from  a 
nozzle  in  the  bottom  of  the  heater  as 
shown  in  the  cut,  and  thereby  absorb- 
ing water  vapor  to  saturation  with  but 
little  excess  of  steam.  In  Fig.  69  is 
illustrated  the  details  of  this  reheater  as 
used  on  the  Nantes,  France,  compressed- 
air  tramway,  in  which  the  compressed 
air  enters  the  heater  at  the  side  near 
the  bottom,  and  is  divided  into  small 
streams  issuing  from  a  perforated  pipe 
and,  bubbling  up  through  the  water,  be- 
comes heated  to  the  temperature  of  the 

water,   and  also  takes   a  considerable    excess   of   hot  vapor  or 
steam,  depending  upon  the  relative  pressures  of  the  air  and  the 

pressure  due  to  the  temperature  of  the 
water. 

A  diaphragm  above  the  water  line 
serves  to  prevent  particles  of  water 
from  escaping  through  the  reducing 
valve  when  thrown  up  by  the  agita- 
tion of  the  passing  air.  The  reduc- 
ing or  regulating  valve  is  of  a  peculiar 
construction  as  shown  in  the  cut.  The 
hand-wheel  when  turned  lowers  or 
raises  a  plunger;  this  acts  upon  a 
liquid  contained  between  it  and  a 
diaphragm  resting  upon  the  head  of 
a  spring  valve  closing  against  the  res- 
ervoir pressure. 

Just  around  the  plunger  there  is  an 
annular  air  space  acting  as  an  air  ves- 
sel      When  the  plunirer  is  depressed 

Fig.    69.— MEKARSKI    KEHEATER.  ^^^-  VV  llCll      LiiK.     ^ii^ii^t,  r 


2  32  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

into  the  liquid,  the  result  is  to  compress  the  air  in  the  air  vessel 
to  anv  desired  extent.  Then,  on  the  air  cock  being  opened, 
air  bubbles  through  the  hot  water,  and  rises  past  the  cone  valve, 
which  is  attached  to  the  diaphragm  into  the  space  below  it,  so 
as  to  press  on  the  under-side  of  the  diaphragm  and  tend  to  raise 
it ;  but  it  cannot  do  so  until  the  pressure  of  the  air  below  the  dia- 
phragm equals  that  in  the  annular  air  vessel  above,  and  thus 
the  pressure  in  the  annular  air  vessel  is  automatically  the  meas- 
ure of  the  pressure  that  will  prevail  in  the  engines.  So  soon  as 
this  is  exceeded  the  diaphragm  rises  and  closes  the  valve;  and 
so  soon  as  it  falls  the  air  in  the  annular  air  vessel  re-expands 
and  lets  in  more  compressed  air.  In  this  way  the  driver  can, 
from  time  to  time,  vary  the  pressure  by  his  hand-vrheel,  confi- 
dent that,  whether  the  engines  are  running  quickly  or  slowly, 
the  pressure  will  be  steadily  maintained.  The  automatic  reg- 
ulating valve  and  the  employment  of  the  "  hot-water  chamber  " 
are  the  distinguishing  features  in  this  particular  system — the 
^Nlekarski  system — of  using  compressed  air. 

The  economic  value  of  reheating  compressed  air  in  close 
proximity  to  an  air  motor  or  engine  by  a  surface  heater  of  the 
Sergeant,  Rand,  or  Edison  type  is  fully  shown  in  column  2  of 
Table  XV.,  which  gives  the  increase  in  volume  from  any  initial 
temperature  to  any  other  temperature  at  which  the  air  emerges 
from  the  heater. 

In  a  surface  heater  of  good  form  the  loss  of  fuel  heat  from 
radiation  and  by  the  smoke-pipe  should  be  no  greater  than  50 
per  cent  of  the  total  heat  value  of  the  fuel,  or,  say  for  coal,  a 
useful  effect  of  ;,ooo  heat  units  per  pound.     This  should  heat 

7-QOO  _  29,  |<^3  pounds  of  air  1°  F.     If  to  be  heated  from  60° 

•2375 

to  360°,  at  which  temperature  the  volum.e  would  be  increased, 

as  found  in  column  2,  Table  XV.,  from  13  cubic  feet  to  20.63 

cubic  feet  per  pound  ;  or  — ^      =  63  per  cent  by  reheating  to  an 

20.63 

amount  of  300^     Then  lM5i  =  94.8  pounds  heated  from  60° 

300 


COiMPRESSED-AIR    REHEATINC;    AND    ITS    WORK. 


233 


to  360°,  and  94.8  X  13  =  1,232.4  cubic  feet  of  initial  free  air, 
heated  from  60°  to  360°  by  i  pound  of  coal.  The  increase  in 
volume  equals  1,232  X  .6^  per  cent,  or  776  cubic  feet.  Then 
if  10  cubic  feet  per  minute  represents  i  horse  power  in  an  air 
motor  at  any  specified  pressure,  there  should  be  a  production 
of  77  horse  power  by  reheating  air  to  an  amount  of  300°  by  the 
burning  of  i  pound  of  coal  per  minute,  or  1.28  of  a  horse 
power  per  i  pound  of  coal  per  hour,  a  far  better  result  than  can 
be  anticipated  from  any  known  condition  of  steam  power. 

When  the  entire  products  of  combustion  are  utilized  there 
is  no  loss  save  radiation,  and  we  can  safely  count  on  90  per 


Fig.  70 —automobile  ueheater. 

cent  of  the  total  heat  units  for  effective  work  in  reheating  com- 
pressed air  for  power.  Thus  by  the  internal  combustion  sys- 
tem the  saving  of  2.4  horse  power  per  pound  of  coal  per  hour 
may  be  accomplished. 

The  method  of  reheating  compressed  air  for  automobile 
motors  is  shown  in  Fig.  70.  The  air  stored  at  high  pressure 
issues  through  a  copper  coil  at  reduced  pressure  controlled  by 
link-valve  gear,  and  reheated  in  its  passage  to  the  motor  by 
gasoline  or  kerosene  burners. 

Small  storage-bottles  of  steel  are  made  to  hold  260  times 
their  volume,  or  .about  4,000  pounds  pressure  per  square  inch. 


;34  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


THE    CALORIC    OR    HOT-AIR    ENGINE. 

The  expansion  and  contraction  of  air  by  the  absorption  and 
elimination  of  its  element  of  heat  give  to  air  a  power  for  work 
which  has  been  utilized  to  a  small  extent  for  motive  power 
during  the  past  century.  The  open-cycle  system  of  its  applica- 
tion in  the  early  motor  engines  did  not  prove  satisfactory  or 
efficient. 

The  most  satisfactory  and  efficient  system  has  been  derived 
from  Carnot's  suggestion  of  the  closed  C3xle  of  heat  transfer  in 
which  the  pressure  element  of  air  is  kept  within  the  motor, 
while  the  heat  element  is  generated  from  the  outside,  trans- 
mitted through  the  enclosed  air  for  work,  and  eliminated  at 
the  cold  end  of  the  cycle  by  a  cooling  medium ;  and  then  the 
air  is  returned  to  the  heat-imparting  chamber  by  the  alternat- 
ing of  two  pistons. 

This  is  the  type  of  the  action  of  the  Ericsson  pumping  en- 
gine with  tandem  pistons  in  a  single  cylinder,  and  the  Rider 
two-cylinder  hot-air  engine.  Other  hot-air  engines  are  of  the 
Roper  type  in  which  the  heat  products  of  combustion  from  an 
internal  furnace  are  absorbed  in  or  mixed  with  the  air  in  its 
open-cycle  progress  through  the  motor,  the  furnace  being  fed 
with  air  from  a  pump  driven  by  the  motor.  The  hot  air  and 
gases  are  exhausted  from  the  cylinder  at  the  close  of  each 
power  stroke. 

wSome  trouble  has  been  found  in  this  class  of  hot-air  motors 
from  the  ashes  lodging  in  the  working  parts,  and  so  clogging 
and  wearing  the  surfaces. 

The  rapid  wear  of  working  surfaces  of  valves  and  cylinder, 
and  the  difficulties  in  properly  lubricating  caused  by  the  intense 
heat  and  ashes,  have  retarded  their  general  use,  apart  from  their 
bulky  proportions. 

The  Stirling  hot-air  engine,  used  in  England  and  on  the 
continent  from  1816  and  further  improved  about  1827,  operated 


COMPRESSED-AIR    REHEATING    AND    ITS    WORK. 


235 


on  the  closed -cycle  system  with  a  regenerator,  using  the  air  at 
constant  initial  volume  with  pressures  due  to  change  of  tem- 
perature and  intensified  by  the  capacity  of  the  regenerator  for 


Fig.  71.— the  ERICSSON  pumping  engine  with  coal-fire  furnace. 

the  absorption  and  elimination  of  heat  from  and  to  the  air  as  it 
passed  between  the  heating  and  cooling  surfaces  in  the  cycle. 
This  engine  required  two  cylinders,  one  of  which  was  the 
power  and  cooling  cylinder,  and  the  other  was  the  heating  cyl- 


236 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


inder  containing  the  transfer  piston.     The  modern  Rider  hot- 
air  engine  is  an  improved  type  of  the  wStirling  engine. 

The  Ericsson  modern  type  of  pumping  engine,  as  made  by 
the  Rider- Ericsson  Engine  Company,  New  York  City,  has  the 
power  piston  and  transfer  piston  working  tandem  in  the  same 


Fig.  72.— section  of  ericsson  pumping  engine,  with  bunsen-burner  gas  furnace. 

I,  Cylinder  ;  2,  air  piston  ;  3,  transfer  piston  ;  4,  heater  ;  5,  furnace  ;  6,  .eras  burners  ;  7,  air 
chamber  ;  8,  main  beam  ;  9,  beam  centre  bearing  ;  10,  connecting  rod  ;  11,  bell-crank  link  ;  12, 
bell  crank  ;  14,  fly-wheel  ;  15,  air  piston  links;  16,  pump  link  ;  17,  pump  chamber;  18,  pump 
gland;  19,  suction  valve;  21.  suction  pipe;  22,  pump  bottom;  25,  crank-shaft  bracket;  26, 
crank  ;  27,  crank  pm  ;  29,  transfer  piston-rod,  cross-head. 


cylinder,  as  represented  in  Figs.  71  and  72.  It  operates  with- 
out a  special  regenerator.  The  hot  air  from  the  heating  cham- 
ber passes  in  a  thin  stratum  along  the  outvSide  of  the  transfer 
piston,  and  is  cooled  in  its  course  toward  the  working  piston  by 
convection  from  the  water-jacketed  surface  of  the  upper  part  of 


COMPRESSED-AIR    REHEATING   AND    ITS    WORK.  237 

the  cylinder,  the  pumped  water  passing  through  the  cylinder 
jacket  for  this  purpose. 

In  the  type  of  the  Rider  hot-air  engine,  operating  through 
the  same  recurring  cycle  and  at  a  constant  initial  volume  with 
differential  heat  pressures,  the  extremes  of  heat  and  cold  are 
established  in  different  cylinders,  the  pistons  being  operated 
from  a  common  shaft  with  cranks  at  right  angles  to  meet  the 
cyclic  requirement,  as  shown  in  the  cut  (Fig.  73).  The  office  of 
the  regenerator  is  to  intensify  the  extreme  temperatures  by 
absorbing  much  of  the  heat  of  the  air  as  it  passes  from  the  heat 
cylinder  to  the  cold  cylinder,  and  to  return  the  same  heat  to  the 
air  in  its  return  from  the  cold  to  the  hot  cylinder.  This  opera- 
tion gives  a  greater  range  to  the  temperature,  and  thereby  in- 
creases the  range  of  pressures. 

Actual  observation  of  the  temperature  at  each  end  of  the 
regenerator  has  shown  a  difference  of  300°  F.,  which  indicates 
a  considerable  differential  pressure,  modified  by  the  propor- 
tional part  of  the  air  volume  in  the  two  cylinders  not  acted 
upon  by  the  regenerator.  This  may  equal  a  mean  differential 
temperature  of  250°  F.  for  the  whole  volume  of  the  enclosed 
air.  The  respective  volumes  will  then  become  as  i  to  1.27, 
and  the  pressures  o  to  4.23  pounds  per  square  inch  during  a 
half  revolution,  with  probably  a  mean  pressure  oi  2}^  pounds 
per  square  inch  during  a  revolution  of  the  fly-wheel.  This  will 
•  be  equivalent  to  about  2,500  foot-pounds,  minute,  in  a  5-inch 
engine,  or  nearly  one-twelfth  of  a  horse  power. 

The  indicator  card  (Fig.  74),  taken  from  a  Rider  two-cylinder 
hot-air  engine  by  Professor  Hutton,  represents  the  cycle  of 
pressures  derived  from  the  apparently  erratic  motion  of  cranks 
at  right  angles  and  operated  by  two  pistons,  both  of  w^hich  were 
under  variable  pressure  from  heat  expansion  in  a  constant  ini- 
tial volume  of  air. 

The  drop  of  the  indicator  line  below  the  atmospheric  line 
during  a  half-stroke  indicates  a  leakage  of  air  under  the  press- 
ure of  three  half-strokes,  or  three-quarters  of  a  revolution. 


238 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  73.— section  of  the  rider  hot-air  pumping  engine. 

A,  Compression  cylinder  ;  B,  power  cylinder  ;  C,  compression  piston  ;  D,  power  piston  : 
£,  cooler  ;  F,  heater  ;  G,  telescope  ;  //,  regenerator  ;  7  7,  cranks  ;  //,  connecting  rods  ;  A'  A', 
piston  packings  ;  /,,  check  valve,  at  back  of  compression  cylinder  ;  J/,  pump  primer  ;  X.  blow- 
off  cock  ;  A",  regenerator  bonnet  ;  .V  5,  pump-valve  bonnet ;  7",  water  jacket,  to  protect  pack- 
ing from  heat ;  C/  U,  pump  buckets  ;   l',  pump  gland. 


COMPRESSED-AIR    REHEATING    AND    ITS    WORK.  239 

The  hot-air  engines  of  the  Ericsson-Rider  type  do  not  oper- , 
ate  on  the  constant-volume  cycle;  for  the  operation  of  the 
working  pistons  varies  the  relative  volumes  by  the  differential 
length  of  the  cranks  and  consequent  amount  of  the  volume  of 
the  stroke,  and  also  does  not  operate  at  constant  pressure; 
hence,  the  heat  volume  of  the  air  is  variable.  At  constant 
pressure  a  motor  piston  cannot  pass  through  a  cyclical  move- 
ment and  do  work.  vSo  that  it  becomes  evident  that  in  the  in- 
vestigation of  the  movement  of  the  pistons  of  this  class  of  en- 
gines,  the  volume  and  pressure    are    both   variable,   and    that 


Fig.  74.— indicator  card. 
Rider  hot-air  engine. 

both  volume  and  pressure  are  made  variable  by  heat  exchange 
and  thus  become  the  elements  of  motive  power. 

In  the  traverse  of  the  two  pistons  in  the  Ericsson  type 
the  transfer  piston  is  neutral  in  pressure,  save  the  air  friction ; 
but  in  the  Rider  type  the  two  pistons  are  of  equal  size,  single 
acting,  both  w^orking  against  the  outer  atmospheric  pressure, 
and  have  the  internal  pressure  equal  on  both  pistons,  save  the 
air  friction  by  transfer.  Its  power  is  derived  from  the  differ- 
ential stroke,  the  transfer  piston  having  the  longest  stroke  by 
about  16  per  cent.  The  Ericsson  hot-air  pumping  engine  is 
made  in  four  sizes,  viz.,  5-,  6-  8-,  and  lo-inch  diameter  of  cyl- 
inder. The  Rider  hot-air  pumping  engine  is  made  in  five 
sizes,  viz.,  4-,  5-,  6-,  8-,  and  lo-inch  diameter  of  cylinders. 


Chapter  XVI. 


THE  COMPRESSED-AIR 
MOTOR 


THE    COMPRESSED-AIR    MOTOR. 

The  published  literature  of  recent  date  on  the  operation 
and  efficiencies  of  compressed-air  motors  and  the  larger  en- 
gines is  too  scant  to  quote  their  actual  work  at  the  present 
time;  and  especially  when  the  engines  of  the  present  day  are 
designed  along  the  lines  of  the  highest  duty  that  can  be  given 
to  the  high-speed  type  and  Corliss  model.  The  operation  of  the 
latter  is  most  desirable  for  obtaining  the  high  efficiency  that 
should  be  expected  from  the  best  designs  and  appliances  for 
generating  compressed  air,  and  for  its  most  useful  work  in  our 
best-constructed  engines  with  reheating  appliances. 

Our  principal  source  of  information  in  regard  to  the  oper- 
ation of  compressed-air  motors  or  engines  is  derived  from  the 
work  of  Professor  Kennedy  and  others  in  their  examinations 
and  experiments  at  the  compressed-air  plant  in  Paris,  France. 
From  the  class  of  compressors  and  motors  in  use  at  that  time 
(1889)  the  results  are  not  satisfactory;  but  it  is  hoped  that  the 
improvements  in  the  efficiency  of  compressors  and  motors  of 
the  present  day  will  enable  us  to  show  a  considerable  increase 
in  the  economy  of  the  use  of  compressed  air  in  compression, 
transmission,  and  for  motive  power,  over  these  conditions  as 
observed  in  the  Paris  plant.  The  small  rotary  engines  in  use 
in  the  Paris  plant  are  convenient  and  compact,  of  high  speed, 
and  use  the  air  with  little  or  no  expansion  and  without  reheat- 
ing, and  of  course  have  no  pretence  to  economy  in  the  use  of 
air.  The  larger-sized  motors  and  engines  of  the  reciprocating 
type  are  of  the  ordinary  slide-valve  gear  with  automatic  cut-off, 
controlled  by  a  governor,  and  mostly  provided  with  reheaters, 
which  have  been  gradually  improved  until  the  later  models 
seem  to  be  very  efficient  in  raising  the  temperature  of  the  ex- 
haust above  the  freezing-point. 


244 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Where  refrigeration  or  cooling  effect  from  the  exhaust  is 
desired,  the  reheater  is  modified  or  dispensed  with.  The  value 
of  reheating  in  the  later  forms  of  the  Paris  apparatus  is  to  raise 
the  temperature  from  175°  to  318°  F.  above  the  normal  tempera- 
ture, or  to  increase  the  volume  of  compressed  air  up  to  60  per 
cent  greater  than  its  normal  volume,  at  a  cost  of  two-tenths  of  a 
pound  of  coal  per  horse-power  hour.     (See  article  on  reheating.) 

In  Fig.  75  is  a  diagram  or  indicator  card  showing  the  con- 
ditions of  air  compression  and  motor  work  of  this  Paris  plant 
as  given  by  Professor  Kennedy.      It  may  be  noticed  in  the  dia- 


FlG.    75.— COMPRESSOR   AND   MOTOR    WORK. 

gram  that  the  compression  was  almost  adiabatic  as  shown  on 
the  double  line  B  C,  showing  want  of  jacket  cooling,  the  upper 
line  B  C  being  adiabatic;  the  closeness  of  these  lines  being 
attributed  partly  to  resistance  in  the  discharge  valves,  so  that 
the  work  of  the  compressors  was  practically  adiabatic.  The 
area  A  B  C  D  E  represents  on  any  scale  the  work  done  in  the 
steam  cylinder,  and  the  area  A  B  C  F  the  work  done  by  the 
same  scale  on  the  air  in  the  compressors.  C  G  is  the  isother- 
mal line  of  compression,  so  that  A  G  represents  the  volume  of 
the  compressed  air  when  it  has  fallen  in  the  mains  to  the  ini- 
tial temperature  at  C  G  H  is  the  adiabatic  curve  of  expansion 
from  the  volume  at  G\  the  area  A  G  H  F  is  61  per  cent  of  the 
area  A  B  C  F  (and  52  per  cent  of  the  area  A  B  C  D  E).     It  rep- 


THE    COMPRESSED-AIR    MOTOR.  245 

resents  the  maximum  work  that  can  be  obtained  in  a  motor 
without  reheating.  Again,  if  the  pressure  falls  from  A  to  A'  by 
transmission,  the  volume  increases  from  A  G  to  K  L,  the  point 
L  lying  on  the  isothermal  line  G  C.  The  loss  of  possible  work 
due  to  such  a  reduction  of  pressure  is  represented  by  the  differ- 
ences between  the  areas  A  G  H  F  and  K  L  M  F,  in  both  of  which 
the  expansion  curves  are  adiabatic.  The  area  K  NOP  repre- 
sents the  actual  work  of  the  motor  without  reheating,  and  the 
area  K  Q  R  P  represents  the  actual 
work  of  the  motor  by  reheating 
the  air  to  320°  F. 

In  Fig.  76  is  shown  a  sample 
card  from  a  10  horse-power  Eng- 
lish engine  which  was  the  subject 

.  •  1  T~>         •  -1  ,  T  FIG-    76.— SLIDE   VALVE   CARD. 

of    test    m    the    Pans   plant,    and 

which  represents  the  area  K  X  O  P  in  the  diagram  (Fig. 
75),  and  with  9.9  indicated  horse  power  was  using  14.8  cubic 
feet  of  free  air  per  horse  power  per  minute.  The  dotted  lines 
are  isothermal,  and  the  contour  of  the  card  shows  defects  in  the 
valves  or  their  motion  and  irregular  adjustment  of  cut-off. 

The  theoretical  power  of  the  air  used  should  have  been  1 1.6 
cubic  feet  of  free  air  per  horse-power  minute,  making  the  indi- 
cated efficiency  of  the  motor  .79;  but  from  undue  weight  and 
friction  of  the  motor  the  mechanical  efficiency  was  but  .67. 

Late  experiments  with  the  rotary  motors  used  in  the  Paris 
compressed-air  system  show  a  most  extravagant  use  of  free  air 
per  horse  power,  viz.,  17.4  cubic  feet  per  horse-power  minute 
with  cold  air,  and  13.9  cubic  feet  when  the  air  was  heated  to 
122°  F,,  with  an  efficiency  of  43  per  cent. 

Many  of  the  motors  now  in  use  in  Paris  have  an  efficiency 
of  only  from  65  to  75  per  cent,  while  a  few  of  the  best  modern 
construction  show  a  mechanical  efficiency  of  91  per  cent.  In 
one  of  the  tests  of  late  date,  on  an  80  horse-power  engine  that 
had  been  used  as  a  steam  engine,  and  for  the  purpose  was  sup- 
plied with  an  air  reheater  in  which  the  temperature  of  the  air 


246  COMPRESSED    AIR   AND    ITS    APl'LICATIONS. 

used  was  320°  F.,  the  engine  used  but  7.54  cubic  feet  of  free 
air  per  horse-power  minute,  correspcnding  to  a  total  efficiency 
of  80  per  cent.  In  this  test  the  consumption  of  coke  for  re- 
heating was  o.  176  pounds  per  horse-power  hour.  The  exhaust 
air  temperature  varied  somewhat  in  difference  with  various 
initial  temperatures  not  readily  accounted  for.  When  the  ini- 
tial temperature  was  305°  F.  the  exhaust  was  84°,  a  difference 
of  22  1°.  With  320°  the  exhaust  was  95°,  difference  225°,  and 
with  338""  the  exhaust  was  120°,  difference  218°. 

For  comparison  with  present  and  future  work  of  compres- 
sion, transmission,  and  work  of  the  motor,  we  give  the  follow- 
ing summary  of  the  efficiencies  of  the  Paris  compressed-air 
plant  as  reported  by  Professor  Kennedy,  from  which  there  has 
been  but  slight  change,  except  perhaps  in  the  later  introduc- 
tion of  more  economical  motors  and  an  increase  in  the  reheat- 
ing temperature : 

One  indicated  horse  power  at  central  station  gives  0.845  in- 
dicated horse  power  in  compressors,  and  corresponds  to  the 
compression  of  348  cubic  feet  of  air  per  hour  from  atmospheric 
pressure  to  ^  atmospheres  absolute. 

Efficiency  of  main  engines,  0.845. 

0.845  indicated  horse  power  in  compressors  delivers  as 
much  air  as  will  do  0.52  indicated  horse  power  in  adiabatic  ex- 
pansion after  it  has  fallen  in  temperature  to  the  normal  tem- 
perature of  the  mains. 

Efficiency  of  compressors     '^''     =  0.61. 
^  ^  0.845 

The  fall  of  pressure  in  mains  between  central  station  and 

Paris  (say   5   kilometers)  reduces  the  possibility  of  work  from 

0.52  to  0.51  indicated  horse  power. 

Efficiency  of  transmission  through  mains  -^  =  0.98. 

The  further  fall  of  pressure  through  the  reducing  valve  to 
41^  atmospheres  (510  atmospheres  absolute)  reduces  the  possi- 
bility of  work  from  0.5  i  to  0.50. 

Efficiency  of  reducing  valve  — ^  =  0.98. 
^  "  0.51 


THE    COMPRESSED-AIR    MOTOR.  247 

The  combined  efficiency  of  the  mains  and  reducing  valve, 
between  5  and  ^.^^  atmospheres,  is  thus  0.98  X  0.98  =  0.96. 
If  the  reduction  had  been  to  4,  ly^,  or  3  atmospheres,  the  cor- 
responding efficiencies  would  have  been  0.93,  0.89,  and  0.85 
respectively. 

Incomplete  expansion,  wire-drawing,  and  other  such  causes 

reduce  the  actual  indicated  horse  power  of  the  motor  from  0.50 

to  0.39. 

Indicated  efficiency'  of  motor  -1^  =  0.78. 

0.50 

Indicated  efficiency  of  whole  process  with  cold  air,  0.39. 

By  heating  the  air  before  it  enters  the  motor  to  about  320° 
F.,  the  actual  indicated  horse  power  at  the  motor  is  increased, 
however,  to  0.54.      The   ratio   of  gain   by   heating  the   air   is, 

therefore,  -^  —  1.38. 

0.39 
Apparent  indicated  efficiency  of  whole  process  with  heated  air, 

0.54. 

In  this  process  additional  heat  is  supplied  by  the  combus- 
tion of  about  0.39  pound  coke  per  indicated  horse  power  per 
hour,  and  if  this  be  taken   into  account  the   real  indicated  effi- 
ciency of  the  whole  process  becomes  0.47  instead  of  0.54. 
Real  indicated  efficiency  of  whole  process  with  heated  air,  0.47. 

Working  with  cold  air  the  work  spent  in  driving  the  motor 
itself  reduces  the  available  horse  power  from  0.39  to  0.26. 

■    Mechanical  efficiency  of  motor,  cold,  0.67. 

Working   with    heated   air   the  work   spent  in    driving   the 
motor  itself  reduces  the  available  horse  power  from  0.34  to  0.44. 
Mechanical  efficiency  of  motor,  hot,  0.81. 

Since  the  first  instalment  of  the  Paris  plant  a  marked  im- 
provement has  been  made  in  the  design  of  the  compressors  of 
a  new  plant,  in  which  two-stage  compression  and  intercooling 
has  been  introduced,  in  which  an  efficiency  of  98  per  cent  is 
claimed  as  between  the  indicated  power  of  the  engine  and 
compressor. 


248  COMPRESSED    AIR    AXU    ITS   APPLICATIONS. 

A    HYDRAULIC    AIR-COMPRESSING    PLANT. 

The  following  abstract  of  a  report  furnishes  some  interest- 
ing details  of  the  air  plant  of  the  North  Star  Mining  Company, 
Grass  Valley,  Cal.,  and  what  has  been  and  can  be  done  through 
the  medium  of  impact  wheels  under  high  water  pressure: 

"  For  this  plant  the  water  supply  is  obtained  from  the  South 
Yuba  Water  Company  at  a  point  on  their  canal  about  four  miles 
froiTi  Grass  Valley,  Nevada  County,  Cal.  Thence  it  is  con- 
veyed about  two  and  one-half  miles  to  the  Empire  ]Mining 
Company's  works  in  a  22 -inch  riveted  iron  pipe,  built  more 
than  ten  years  ago.  The  new  conduit  is  a  riveted  steel  pipe, 
20  inches  in  diameter,  joined  to  the  lower  end  of  this  old  one 
under  a  head  of  420  feet,  and  continues  7,070  feet  to  the  power- 
house, situated  at  the  lowest  convenient  point  on  Wolf  Creek, 
just  below  the  town  of  Grass  Valley,  where  a  head  of  775  feet, 
or  a  static  pressure  of  335  pounds  per  square  inch,  is  obtained. 
The  capacity  of  this  pipe  is  sufficient  to  develop  800  to  1,000 
horse  power. 

"At  the  powxr-house  there  is  a  Pelton  water-wheel,  18 
feet  6  inches  in  diameter,  running  on  a  lo-inch  shaft,  to  which 
a  duplex  compound  air  compressor  is  connected  directly.  The 
initial  cylinders  are  18  inches,  and  the  second  cylinders  are  10 
inches  in  diameter  with  a  24-inch  stroke.  They  were  designed 
to  run  at  1 10  revolutions  per  minute,  and  require  28^^  horse 
power  from  the  water-wheel. 

"  A  6-inch  lap-welded  pipe  conveys  the  air  at  90  pounds 
pressure  from  the  power-house  to  the  compan3''s  Stockbridge 
shaft  on  Massachusetts  Hill,  800  feet  distant  and  125  feet 
higher.  Here  it  is  being  used  in  a  100  horse-power  cross- 
compound  Corliss  pneumatic  hoisting  engine,  and  a  75  horse- 
power compound  pump,  beside  other  pumps,  blacksmith  forge, 
drills,  etc. 

"  About  1,000  feet  from  the  lower  end  a  12-inch  branch  with 
a  gate  is  put  in  for  possible  future  use,  and  near  it  is  a  20-inch 


THE    COMPRESSED-AIR    MOTOR.  249 

gate.  At  the  lower  end  of  the  pipe  in  the  power-house  there 
is  another  20-inch  gate,  below  which  is  a  12 -inch  branch  lead- 
ing to  the  Pelton  wheel,  and  adjoining  this  is  the  receiver,  2 
feet  in  diameter,  on  which  are  the  air  chambers,  charging  tube, 
and  relief  valve.  The  air  chamber  is  a  lo-inch  lap- welded  tube 
18  feet  long  standing  on  the  receiver,  with  an  8-inch  gate  be- 
tween. The  charging  tube  is  similar,  but  8  inches  in  diameter. 
Both  have  2-inch  water  discharge  pipes  and  gates,  and  by 
proper  manipulation  of  the  gates  and  the  operation  of  inlet 
check  valves  on  top  of  the  tubes,  the  air  chamber  may  be  filled. 
Ordinarih'  the  charging-tube  is  filled  up  to  90  pounds  pressure 
from  the  air  compressor  delivery  pipe,  and  then  raised  by  the 
water  pressure.  It  is  found  necessary  to  put  in  about  one-tenth 
of  the  volume  of  the  air  chamber  every  day.  Where  the  air 
goes  is,  thus  far,  a  mystery,  as  no  leak  has  been  discovered." 
This  should  be  no  mystery,  for  it  is  well  known  that  water 
under  great  pressure  absorbs  a  large  addition  to  its  natural 
holding  under  atmospheric  pressure.  "The  demand  for  direct 
action  under  a  head  of  775  feet  made  a  large  wheel  necessary  in 
order  to  obtain  the  proper  peripheral  speed  of  half  the  spouting 
velocity.  This  could  not  readily  be  done,  and  a  wheel  of  18)^ 
feet  diameter  was  made  by  the  Pelton  Company  of  San  Francisco, 
who  guaranteed  an  efficiency  of  85  per  cent  of  the  water  value 
at  full  load,  and  an  average  of  75  per  cent  from  half  to  full  load 
of  the  theoretical  power  of  the  water,  and,  at  the  same  time,  to 
so  govern  the  wheel  that  it  should  not  exceed  120  revolutions 
nor  raise  the  air  pressure  above  105  pounds  per  square  inch  in 
case  of  accident  to  machinery  or  sudden  shutting-off  of  air. 
The  rim  is  built  up  of  angles  and  plates  riveted  together  to 
break  joints.  It  weighs  about  6,800  pounds,  and  is  held  con- 
centric with  the  shaft  by  twelve  pairs  of  radial  spokes  of  i^^- 
inch  rod  iron  held  by  nuts  to  the  cast-iron  hub.  The  driving 
force,  being  applied  to  the  rim,  is  transferred  to  the  hub  by 
four  pairs  of  2 -inch  iron  rods,  so  arranged  as  to  form  a  truss. 
The  wheel  is  set  on  a  lo-inch  shaft,  having  a  disc  crank  on 


250  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

either  end  and  connected  directly  to  the  compressors.  The 
regulator  is  a  floating-  valve  actuated  against  excessive  velocity 
by  the  ordinary  ball  governor  and  against  excessive  air  press- 
ure by  a  spring  set  to  move  when  the  air  pressure  in  the  de- 
livery pipe  exceeds  90  pounds. 

"  Repeated  tests  which  checked  very  closely  give  the  wheel 
an  efficiency  of  a  trifle  over  90  per  cent  for  one-quarter,  one- 
half,  three-quarters,  and  full  loads.  Between  these  points  it  is 
somewhat  less,  as  the  hood  coming  down  over  the  nozzle  tends 
to  deflect  the  water  as  well  as  hold  it  back,  and  decreases  the 
efficiency.  It  seems  probable  that  the  long  radius  of  the 
wheel  accounts  for  the  high  efficiency. 

"The  compressors  were  built  by  the  Fulton  Engineering 
and  vShip-Building  Company  of  San  Francisco.  They  are  made 
very  heavy,  to  stand  the  high  piston  speed  required  by  the  con- 
ditions of  the  water  power.  The  compressor  cylinders  are  18 
and  10  inches  in  diameter  and  24  inches  stroke. 

"  The  most  novel  feature  of  these  machines  is  the  inter- 
cooler.  This  is  made  up  of  forty-nine  soft  copper  pipes,  i  inch 
in  diameter,  18  feet  lono-,  each  with  a  stuffing-box  at  each  end 
connected  with  manifold  castings.  The  air  delivered  from  the 
first  cylinder  into  one  manifold  passes  through  these  pipes  to 
the  other  manifold,  from  which  it  is  taken  to  the  second  cylin- 
der. The  whole  is  placed  in  the  wheel  pit  directly  under  and 
in  front  of  the  wheel,  so  that  the  water  dashes  all  over  and 
through  it.  The  air,  leaving  the  first  cylinder  at  a  temperature 
of  200°  F.,  passes  through  the  intercooler  and  enters  the  second 
cylinder  at  60°,  slightly  cooler  than  when  entering  the  first  cyl- 
inder. The  temperature  is  again  raised  to  204°  on  leaving  the 
second  cylinder  and  passing  into  the  transmission  pipe,  show- 
ing a  total  rise  in  temperature  of  282°  F.  from  both  stages. 

"The  transmission  pipe,  conducting  the  air  at  90  to  100 
pounds  pressure  about  800  feet  from  the  compressors  to  works 
at  the  mine,  is  ordinarily  well  tubing  53^'  inches  in  diameter 
inside.      At  the  mine  there  is  the  ordinary  air    receiver    and 


THE    COMPRESSED-AIR    MOTOR.  25  I 

also  three  50-horse-power  boilers  set  ready  for  steam,  which  are 
used  for  receivers. 

"  The  air  is  taken  from  these  into  the  reheaters.  It  requires 
a  little  over  half  a  cord  of  good  pine  wood  each  twenty-four 
hours  to  heat  about  700  cubic  feet  of  free  air  per  minute  to  a 
temperature  350°  to  400°  F.  The  heated  air  passes  through 
pipes  covered  with  magnesia  and  hair-felt  to  the  first  cylinder 
of  the  hoisting  engine,  from  which  it  is  exhausted  back  into 
the  upper  heater,  where  its  temperature  is  again  brought  to 
350°,  whence  it  jDasses  to  the  second  cylinder  at  30  pounds  press- 
ure. From  this  it  is  exhausted  through  a  flue  to  the  change 
house,  where  it  is  used  for  heating  and  drying  clothes.  From 
the  first  heater  also  the  air  for  the  pump  is  conveyed  some  300 
feet  down  the  shaft  in  a  similarly  covered  pipe.  It  receives 
the  air  at  about  275''  and  exhausts  it  into  the  shaft  at  about  60°, 
thus  giving  plenty  of  pure  cool  air  to  the  men,  without  the 
usual  fans  or  ventilators. 

"  A  direct-acting  donkey  pump  is  situated  in  another  shaft 
750  feet  distant,  to  which  air  is  carried  cold  in  a  2-inch  pipe 
over  the  surface.  An  old  hot-water  heater  is  used  as  a  reheater 
for  the  air,  and  consumes  twelve  sticks  of  pine  cord-w^ood  per 
twenty-four  hours. 

"  The  hoisting  engine  is  a  compound  direct-acting  Corliss  of 
100  horse  power  with  cylinders  jacketed  for  hot  air,  and  is  cal- 
culated to  work  3,000  feet  down  an  incline  of  about  35°. 

"  There  is  304  theoretical  horse  power  in  the  water  used  at 
the  power-house,  the  work  aactuall}'  accomplished  at  the  mine 
amounts  to  203  horse  power,  and  the  cost  of  reheating  is  $3 
per  day. 

"  Efficiency  of  compression  and  transmission  from  water 

wheel  to  motors,  and  not  including  cost  of  reheating  — ^l?_  =  79.5  per  cent. 

283 
Efficiency  of  compression  and  transmission  from  theoret- 
ical power  of  the  water  to  the  motors,  and  not  in- 
cluding cost  of  reheating ".lllA"  =  74  per  cent. 

304 
Efficiency   from    the   water-wheel    to    and    througli    tlie 

^  20''  7 

motors,  not  including  reheating '-  =  Ji-b  per  cent. 

2S3 


252  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

Efficiency    from   the   llieoreUcal  power  of    tlie  water,    to 
and  through   the  motors,  and  not  inchiding  the  cost 

"^  20''   7 

of  reheating — ^  =  66  per  cent. 

304 
Efficiency  of  compression  and  transmission  from  water- 
wheel  to  motors,  including  the  cost  of  reheating  ex- 

pressed  in  water  power -^'^^  =  7^  per  cent. 

307.66 
Efficiency  of  compression  and  transmission  from  the  the- 
oretical power  of  the  water  to  the  motors,  including 

2'"i   "^2 

the  cost  of  reheating  expressed  m  water  power — ^^r_  —  68.4  per  cent. 

329 
Efficiencv    of    compression    and   transmission   from    the 

water-wheel  to  and  through  motors,   including  cost 

of  reheating  expressed  in  water  power — — ^  =  65. 5  per  cent. 

307.66 
Efficiency  of  compression  and  transmission  from  the  the- 
oretical power  of  water  to  and  through  the  motors,  ^ 
including  cost  of  reheating  expressed  in  water  power.    — —  =  ^^-^  P^i"  cent. 

Horse  power  of  air  at  works  after  reheating 225.32 

Horse  power  delivered  to  compressors  by  water-wheel 283 

Theoretical  horse  power  of  water  used  on  the  wheel 304 

Horse  power  of  work  actually  done  by  the  motors 202. 7 

The   horse   power   delivered    by  the   water-wheel    to    the 

compressor,  to  which  is  added  the  horse  power  (24.66) 

which  the  cost  of  the  wood  used  in  reheating  would 

buy  in  water „ 307.66  =  283  -|-  24.66 

The  theoretical  horse  power  of  the  water  used  on  wheel 

added  to  the  horse  power  (24.66)  which  the  cost  of  tiie 

wood  used  in  reheating  would  buy  in  water 329  =  304  -|-  24.66  " 

It  may  be  urged  that  the  conditions  are  particularly  favor- 
able to  compre.ssed  air,  as  the  transmission  is  short  and  the 
power  is  not  needed  for  tramways  or  lighting.  But  were  it  20 
miles  instead  of  1,000  feet,  it  is  thought  by  the  author  that, 
taking  the  w'hole  plant,  compres.sor,  transmission  pipe,  and 
motor,  as  against  generator,  transmission  wires,  transformers, 
and  electric  motors,  the  air  will  prove  cheaper  in  first  cost, 
higher  in  efficiency,  less  liable  to  accident,  and  less  expensive 
to  operate  and  maintain  than  by  electric  transmission  and 
power. 

The  hydraulic  power  air  plant  of  the  hydraulic  power  com- 
pany at  Iron  Mountain,  Mich.,  is  said  to  be  the  largest  com- 
pressed-air plant  in  the  United  vStates.  It  utilizes  the  water- 
power  of  the  Quinnesec  Falls,  which  are  47  feet  high.  A 
separate  turbine  operates  three  duplex  compressors  32  x  60 
inches  and  one  duplex  compressor  36  x  60  inches,  with  a  capac- 


THE    COMPRESSED-AIR    MOTOR. 


253 


ity  of  about  16,000  cubic  feet  of  free  air  per  minute  compressed 
variably  from  62  to  67  pounds  pressure  per  square  inch.  The 
compressed  air  is  transmitted  3  miles  through  a  24-inch  conduit, 
with  loss  in  pressure  of  from  2  to  3  pounds  per  square  inch, 
and  then  distributed  through  1,500  feet  of  variable-sized  pipes 
to  hoisting  engines,  air  pumps,  rock  drills,  and  engines  for  run- 
ning dynamos  for  electric  lighting. 

In  Fig.  ']'/  is  a  reduced  copy  of  an  indicator  card  from  an 
automatic  Corliss  engine,  10  x  30  inches,  86  revolutions,  and  65 
pounds  pressure  in  the  air  pipe;    air  at  normal  temperature  of 


Fig    77  -  CORLISS  t.ngine  air  card, 

70°  F.  ;  cut-off  .175,  which  with  4  per  cent  clearance  makes  the 
real  cut-off,  as  per  Table  XXII.,  .206,  for  which  the  theoretical 
mean  pressure  should  be,  for  the  air  entrance  pressure  of  59 
pounds,  73.7  X.4369  =  32.19  —  14.7  =  17.49  pounds,  the  mean 
pressure.  By  the  indicator  card  the  measured  mean  pressure 
of  the  head  end  is  found  to  be  19.21.  The  dotted  lines  on  the 
card  show  the  theoretical  adiabatic  curve,  the  terminal   press- 


ire  of  which  is  shown  bv  the  formula,  'ji.'j  X.1041 


l-(^7 


14.7  =  —  6.03.  The  final  temperature  of  the  exhaust  should 
have  been  by  the  ratio  for  volumes  from  70°  F.  expanded  from 
.206  real  cut-off  .5192  X  530°  =  275  —  460  =  —185°  F. 

The  ratios  may  be  taken  from  Tables  XVI.   and  XVII.   for 
small  divisional  parts  by  interpolation  ;  or  the  terminal  temper- 

ature  may  be  obtained  from  the  equation  ( -„- )     •    R  the  ratio 


254 


COMPRESSED   AIR    AND    ITS   APPLICATIONS. 


is =  4.854  log.  0.6861   X  .408  =  0.27992,  index  of  which 

.206 


is  1.905  and 


1.905 


=  .5248  X  530°  =  278  -  460°  =  -  182°  F. 


The  indicator  card  (Fig.  78)  is  from  the  same  engines  as 
above,  with  a  pressure  of  58  pounds  in  the  air  pipe,  valve  partly 
throttled  so  that  the  entrance  pressure  was  but  48  pounds,  and 
the  cut-off  automatically  extended  to  .22  and  the  real  cut-off  by 
the  clearance  .25.     The  air  was  taken  through  a  reheater  and 


Li  11^ 


Fig.  78.— CORLISS  engine  air  card. 

entered  the  cylinder  at  a  temperature  of  310°,  making  the  mean 
pressure  by  measurement  but  slightly  less  than  the  previous 
card,  and  exhausting  below  the  atmospheric  pressure  about  i^ 
pounds  and  6  pounds  above  the  adiabatic  theoretical  line  as 
shown  by  the  dotted  line.  The  final  temperature  as  found 
from  the  ratio  of  expansion,  which  is  4  log.  0.60206  X-4o8  = 


0.24564,  index  1.761,  and 


1. 76 1 


=  .5678  X  770  =  437  -  460  = 


-0 


Chapter  XVII. 


EFFICIENCY  OF  AIR 

COMPRESSORS  AT  HIGH 

ALTITUDES 


EFFICIENCY   OF    AIR    COMPRESSORS   AT    HIGH 
ALTITUDES. 

As  the  density  of  the  atmosphere  decreases  with  the  alti- 
tude, a  compressor  located  at  a  high  altitude  takes  in  less  air  at 
each  revolution,  that  is  to  say,  the  air  is  taken  in  at  a  lower 
pressure ;  hence  the  early  part  of  each  stroke  is  occupied  in 
compressing  the  air  from  the  lower  density  up  to  the  normal 
sea  level  pressure  of  14.7  pounds,  and  the  volumetric  capacity 
of  the  air  cylinder  is  correspondingly  diminished.  The  power 
required  to  drive  the  same  compressor  is  also  less  than  at  sea 
level,  but  the  decrease  in  power  required  is  not  in  as  great  a 
ratio  as  the  reduction  in  capacity.  Therefore,  compressors  to 
be  used  at  high  altitudes  should  have  the  steam  and  air  cylin- 
ders properly  proportioned  to  meet  the  varying  conditions  at 
different  altitudes.  The  compressor  friction  and  leakage  losses 
are  a  constant  quantity. 

It  is  apparent  that  the  densej"  the  air  is  when  drawn  into  the 
compressor  cylinder,  the  sooner  the  desired  pressure  is  reached 
in  terms  of  the  cylinder  stroke,  and,  on  the  contrary,  the  lighter 
or  less  dense  the  air  is  at  the  intake,  the  smaller  will  be  the 
volume  at  the  desired  pressure,  or  the  pressure  is  reached  at  a 
later  point  in  the  stroke.  The  volumetric  efficiency  of  an  air 
compressor  will  therefore  be  inversely  as  the  mean  pressure, 
and  the  loss  of  capacity  will  be  the  complement  of  the  efficiency. 

The  air  temperature  at  high  levels  is  on  the  average  lower 
than  at  sea  level  throughout  the  year,  which  slightly  increases 
the  density  due  to  the  height  alone ;  so  that  the  volumetric 
efficiency  may  be  somewhat  higher  than  is  due  to  barometric 
pressure  alone. 

The  decreased  power  required  by  a  compressor  due  to  ele- 
vation varies  from  60  to  56  per  cent  of  the  loss  of  capacity. 


258 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


The  following  table  shows  the  efficiency  and  loss  in  capacity 
of  compressors  working  at  different  altitudes,  also  the  approxi- 
mate decrease  in  power  required  as  compared  with  the  same 
compressor  working  at  sea  level,  and  delivering  air  at  70  pounds 
pressure  per  square  inch  : 

TABLE   XXXIII. — Compressor  Efficiencies  at  Different  Altitudes. 


Barometric  Pressure. 

Volumetric 

efficiency  of 

compressor, 

per  cent. 

Loss 
of  capacity, 
per  ce,nt,"    f 

Decreased 

Altitude,  feet. 

Inches, 
mercury. 

Pounds  per 
square  inch. 

required, 
per  cent. 

0 

1,000 

30.00 

28.88 
27.80 
26.76 
25-76 

24-79 
23.86 

22.97 

22.11 
21.29 
20.49 
19.72 
18.98 
18.27 

17-59 
16.93 

14-75 
14.20 

13-67 
13.16 
12.67 
12.20 

"•73 
11.30 
10.87 
10.46 
10.07 
9.70 

9-34 

8.98 
8.65 
8.32 

100 
97 
93 
90 

87 
84 
81 
78 
76 
73 
70 
68 
65 
63 
60 
58 

0 
3 

7       ' 

TO 

13 
16 

19 
22 

24 

27 
30 
32 

35 
37 
40 

42 

0. 

1.8 

2,000 

3-5 

5-2 

6.9 

8-5 

a.  000 

4, 000 

5,000 

6, 000  

10. 1 

7, 000 

II. 6 

8,000. 

13- 1 
14.6 
16. 1 

Q ,  000 

10,000  

11,000  

17-6 
19. 1 
20.6 
22.1 

23-5 

12,000 

13,000 

14,000 

15,000 

For  pressures  above  70  pounds  as  given  in  above  table,  de- 
duct 3  per  cent  from  the  tabulated  figures  in  column  4  and  10 
per  cent  in  column  6  for  each  10  pounds  approximate. 


CAPACITY    OF   AIR    COMPRESSORS. 

To  ascertain  the  capacity  of  an  air  compressor  in  cubic  feet 
of  free  air  per  minute,  the  common  practice  is  to  multiply  the 
area  of  the  intake  cylinder  by  the  feet  of  piston  travel  per  min- 
ute. The  free  air  capacity  of  the  compressor  divided  by  the 
number  of  atmospheres  will  give  the  volume  of  compressed  air 
per  minute.  To  ascertain  the  number  of  atmospheres  at  any 
given  pressure,  add  15  pounds  to  the  gauge  pressure,  divide 
this  sum  by  15,  and  the  result  will  be  the  number  of  atmos- 
pheres. 

The  above  method  of  calculation,  however,  is  only  theoret- 
ical, and  these  results  are  never  obtained  in  actual  practice  even 


EFFICIENCY    OF   AIR    COMPRESSORS   AT    HIGH    ALTITUDES.       259 

with  compressors  of  the  very  best  design.  Allowances  should 
be  made  for  losses  of  various  kinds,  the  principal  loss  being 
due  to  clearance  spaces ;  but  in  machines  of  poor  design  and 
construction  other  considerable  losses  occur  through  imperfect 
cooling,  leakages  past  the  piston  and  through  the  discharge 
valves,  and  insufficient  area  and  improper  working  of  inlet 
valves.  We  have  seen  compressors  in  which  the  total  air  loss 
was  from  10  to  20  per  cent,  whereas  3  to  10  per  cent  should  be 
the  maximum — according  to  size— in  compressors  of  best  de- 
sign and  construction. 

The  following  table  will  be  found  useful  for  ascertaining 
quickly  the  capacity  of  an  air  compressor,  also  to  find  the 
cubical  contents  of  any  cylinder  or  receiver. 

The  first  column  is  the  diameter  of  the  cylinder  in  inches, 
the  second  shows  the  cubical  contents,  in  feet,  for  each  foot 
in  length.  To  find  the  capacity  of  an  air  cylinder,  multiply  the 
figure  in  the  second  column  by  the  piston  travel  in  feet  per 
minute ;  this  applies  to  double-acting  air  cylinders ;  in  the  case 
of  single-acting  air  cylinders  the  result  should  be  divided  by  2. 


TABLE   XXXIV. 


-Contents  of  Cylinder   in  Cubic    Feet  for  Each  Foot  in 
Length. 


Diam. 

Cubic 

1  Diam. 

Cubic 

Diam. 

Cubic 

Diam. 

Cubic 

Diam. 

Cubic 

inches. 

contents. 

inches. 

contents. 

inches. 

contents. 

inches. 

contents 

inches. 

contents. 

I 

.0055 

5^ 

.1803 

loyi 

.6013 

i8>^ 

1.867 

31 

5-241 

iX 

.0085 

6 

.1963 

lOX 

.6303 

19 

1.969 

32 

5-585 

I>^ 

.0123 

ex 

.2130 

II 

.6600 

19K 

2.074 

33 

5-940 

I^ 

.0168 

t% 

.2305 

iiX 

.6903 

20 

2.182 

34 

6.305 

2 

.0218 

6|^ 

.2485 

11% 

■7213 

20>^ 

2.292 

35 

6.681 

2X 

.0276 

7 

.2673 

11^4 

■7530 

21 

2.405 

36 

7.069 

2>^ 

.0341 

7X 

.2868 

12 

•7854 

2I>^ 

2.521 

37 

7-468 

23/ 

•0413 

1% 

.306S 

12K 

.8523 

22 

2.640 

38 

7.886 

3 

.0491 

IVat 

.3275 

13 

.9218 

22>^ 

2.761 

39 

8.296 

3% 

.0576 

8 

•3490 

13K 

.9940 

1    23 

2.885 

40 

8.728 

3% 

.0668 

8X 

•3713 

14 

1.069 

23>^ 

3.012 

41 

9.168 

3U 

.0767 

8K 

•3940 

l^Vz 

1.147 

24 

3-142 

42 

9.620 

4 

.0873 

8^ 

•  4175 

15 

1.227 

25 

3-409 

43 

10.084 

4^ 

.09S5 

9 

.4418 

nVz 

1. 310 

26 

3.687 

44 

10. 560 

4.5^ 

.1105 

9X 

.4668 

16 

1.396 

27 

3-976 

45 

11.044 

4^4 

.1231 

9% 

.4923 

i6j^ 

1.485 

28 

4.276 

.\b 

11.540 

5 

.1364 

9^ 

.5185 

17 

1-576 

29 

4-587 

47 

12.048 

s% 

•  1503 

10 

•5455 

17,'^ 

1.670 

30 

4.909 

48 

12.566 

5>^ 

.1650 

loX 

•5730 

18 

1.767 

26o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


COMPRESSED    AIR    FOR    HOISTING    ENGINES. 

The  following-  table  is  intended  to  give  an  approximate  idea 
of  the  volume  of  free  air  required  for  operating  hoisting  en- 
gines, the  air  being  delivered  to  the  engines  at  60  pounds 
gauge  pressure.  There  are  so  many  variable  conditions  to  the 
operation  of  hoisting  by  the  hoisting  engines  in  common  use 
that  accurate  computations  can  only  be  offered  when  fixed  data 
are  given.  In  the  table,  the  hoisting  engine  is  assumed  to 
actually  run  but  one-half  of  the  time  for  hoisting,  while  the 
compressor,  of  course,  runs  continuously.  If  the  engine  run 
less  than  one-half  the  time,  as  it  usually  does,  the  volume  of 
air  required  will  be  proportionately  less,  and  vice  versa.  The 
table  is  computed  for  maximum  loads,  which  also  in  practice 
may  vary  widely.  From  the  intermittent  character  of  the  work 
of  a  hoisting  engine  the  parts  are  able  to  resume  their  normal 
temperature  between  the  hoists,  and  there  is  little  probability 
of  the  annoyance  of  freezing  up  the  exhaust  passages. 

TABLE  XXXV. — Volume  ok  Free  Air  Required  per  Minute  for  Operating 
Hoisting  Engines,  the  Air  Compressed  to  60  Pounds  Gauge  Pressure. 


Single   Cylinder  Hoisting  Engine. 


Diameter 

of  cylinder, 

inches. 


Stroke, 
inches. 


Revo- 
lutions 

per 
minute. 


Normal 
horse- 
power. 


Actual  Weight 

horse-     i       lifted, 
power.       single  rope. 


Cubic 
feet  of  free 

air 
required. 


5  . 
5 

6X 
7  . 
8X 

ID 


6 
8 
8 

10 
10 
12 
12 


200 
160 
160 
125 
125 
no 
no 


3 

4 

6 

10 

15 
20 

25 


5-9 

6.3 

9.9 

12. 1 

16. 8 
18.9 
26.2 


600 
1,000 
1,500 
2,000 
3,000 
5,000 
6,000 


75 
80 

125 
i5r 
170 

23S 


Double  Cylinder  Hoisting  Engine. 


5  ■ 
5  . 
b%. 

7  • 
8X. 

10 

12X. 
14  . 


6 

200 

6 

n.S 

8 

160 

S 

12.6 

8 

160 

12 

1 9. 8 

10 

125 

20 

24.2 

10 

125 

30 

33-6 

12 

no 

40 

37.8 

12 

no 

5" 

52.4 

15 

100 

75 

89.2 

18 

90 

100 

125- 

1. 000 
1,650 
2,500 
3.500 

6, 000 

8, 000 

10,000 


150 
160 
250 
302 
340 
476 
660 
1,125 
1,587 


AIR    FOR   PUMPS   AND    MOTORS. 


261 


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262 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


To  find  the  amount  of  air  and  pressure  required  to  pump  a 
given  quantity  of  water  a  given  height,  find  the  ratio  of  diame- 
ters between  water  and  air  cylinders,  and  multiply  the  number 
of  gallons  of  water  b}'  the  figure  found  in  the  column  for  the 
required  lift.  The  result  is  the  number  of  cubic  feet  of  free 
air.  The  pressure  required  on  the  pump  will  be  found  directly 
above  in  the  same  column.  For  example:  The  ratio  between 
cylinders  being  2  to  i.  Required  to  pump  100  gallons,  height 
of  lift  250  feet.  Find  under  250  feet  at  ratio  2  to  i,  the  figures 
2. 1 1  :  then  2. 1 1  X  100  =  2  ri  cubic  feet  of  free  air  for  the  time 
required  to  lift  the  water,  or  per  minute  for  both  water  and 
air.     The  pressure  required  is  34.38  pounds. 


TABLE     XXXVII. — Volume    of    Air    and    Pressure    Required    to    Drive 
Direct-Acting  Steam  Pumps.  (F.  C.  Weber.) 


Gauge  Pressures  in  Pounds  per     Ci 
Square  Inch. 

;bic  Feet  of  Free  Air  per  Minute  to 
Lift  One  Gallon  of  Water. 

rt 

H 

Ratio  of  Cylinder  Diameters. 

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0 

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6 
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36 
42 
47 
52 
65 
78 
90 
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22 

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33       -42 
38       .47 
44       -53 
49       -58 
54       ■f>3 
61       .68 
66      .75 
72      .82 
86      .95 
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12     1.22 
28     1.37 
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..     1.92 

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1.63 

1.75 
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4.00 
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1.67 
1.88 
2.00 
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2.95 
3.22 

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3.82 

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5.00 
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6.00 
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20 

7 
10 

13 
17 
20 

23 
26 
30 
34 
42 
50 
58 
67 

83 
100 

30 
40 
50 
60 

7 

9 

12 

14 
16 

18 
21 
23 
29 
35 
40 
46 
58 
68 
80 
92 
105 

7 
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12 
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15 
17 
21 

25 
30 
34 
42 
50 
58 
67 
75 
85 
100 

7 
8 

9 
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13 
16 
20 

23 
26 

33 
39 
45 
52 
58 
65 
78 
92 
105 

70 
80 

QO 
100 

I2i5 

150 

175 
200 
250 
300 
350 
400 
450 
500 
600 

10 
13 
15 
17 
21 
25 
29 
33 
37 
42 
50 
60 
67 
75 
85 

9        I. 
10       I. 
12         I. 
15         .. 
17 
20 

23         .. 
26         .. 
29         .. 

35      .. 
42      .. 
47      .. 
52      . 
58      .. 

2.31 
2.40 
2.60 

2.89 
3.08 

3-37 

3.66 

3.95 

4.24 

4.80 

700 
800 

5- 50 

5.96 

900 
1,000 

6-45 

7.00 

AIR    FOR    PUMPS   AND    MOTORS.  263 

To  find  the  quantity  of  free  air  required  per  minute,  in  a 
direct-acting  steam  pump,  to  raise  a  given  number  of  gallons  of 
water  through  a  given  head,  divide  the  diameter  of  air  cylinder 
by  the  diameter  of  water  cylinder,  and  under  the  heading  of 
this  ratio  in  above  table  and  to  the  right  of  the  given  head  or 
lift  find  the  cubic  feet  of  free  air  per  gallon  required  per  min- 
ute; this  constant  multiplied  by  the  total  number  of  gallons  to 
be  lifted  will  give  the  quantity  of  free  air  required.  The  gauge 
pressure  for  the  corresponding  conditions  can  be  found  in  a  sim- 
ilar manner  under  the  heading  of  gauge  pressures. 

In  the  above  table  of  pressures  an  allowance  of  1 5  per  cent 
has  been  made  for  pump  friction,  and  in  the  table  of  volumes 
1 5  per  cent  has  also  been  allowed  for  clearance  losses  and  leak- 
age. If  the  air  is  reheated  before  admission  to  air  cylinder  the 
quantity  may  be  reduced  in  proportion  to  the  ratio  of  absolute 
temperatures.  For  compound  pumps  the  consumption  may  be 
assumed  at  75  per  cent  of  the  best  results  of  the  above  table. 

To  find  the  amount  of  air  required  to  drive  any  steam  pump 
under  any  head  of  water :  Divide  the  diameter  of  the  air  cylin- 
der by  the  diameter  of  the  water  cylinder,  find  the  ratio  in  the 
first  column  of  Table  XXXVIII. ,  follow  the  line  of  figures  to  the 
right  until  the  column  is  reached  which  is  headed  by  the  head 
of  water  to  be  pumped  against.  At  this  point  will  be  found  a 
constant  which,  multiplied  by  the  area  of  the  air  piston  in 
square  inches,  will  give  the  cubic  feet  of  free  air  consumed  by 
the  pump  per  minute,  at  100  feet  piston  speed  per  minute. 

AIR    VOLUMES    USED    IN    ENGINES   AND    MOTORS. 

The  present  increasing  demand  for  the  use  of  compressed 
air  as  a  motive  power  necessarily  involves  the  use  of  intricate 
mathematical  formulae  for  estimating  relative  sizes  of  compres- 
sors and  air  engines. 

Quite  a  number  of  these  formulae  have  been  worked  out  to 
cover  average  practical  conditions  and  are  daily  serving  a  very 
useful  purpose  in  the  form  of  tables. 


264 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


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AIR    FOR    PUMPS   AND    MOTORS. 


265 


A  very  intricate  formula  is  the  one  based  upon  the  use  of 
free  air  per  minute  per  indicated  horse  power  in  an  air  engine, 
and  as  a  problem  is  often  stated  in  terms  of  the  I.  H.  P.  of  the 
motor — to  find  the  quantity  of  free  air  per  minute  required;  the 
following  table  will  facilitate  computations  of  this  kind  and  is 
in  such  shape  that  it  will  not  require  any  extended  knowledge 
of  mathematics : 


TABLE    XXXIX.— Air    Used    in    Cubic    Feet    Free    Air    per    Minute,    per 
I.  H.  P.  IN  Motors   (Without  Reheating). 


Gauge  Pressures. 

P  3 

3°- 

40. 

50. 

60. 

70. 

80. 

90. 

100. 

no. 

125. 

150. 

I 

23-3 

21.3 

20.2 

19.4 

18.8 

18.42 

18.10 

17.S 

17.62 

17-40 

17.05 

1 

18.7 

17.1 

16. 1 

15-47 

15.0 

14.6 

14.35 

14-15 

13-98 

13-78 

13-50 

1 

17.85 

16.2 

15-2 

14.50 

14.2 

13-75 

13-47 

13-28 

13.0S 

12.90 

12.60 

■l 

16.4 

14.S 

13-5 

12.8 

12.3 

11-93 

[1. 7 

11.48 

11.30 

II. 10 

10.85 

^ 

17-5 

15.2 

12.9 

11.85 

11.26 

10.8 

10.5 

10.21 

10.02 

9. 78 

9- 50 

^ 

20.6 

I5.b 

13-4 

13-3 

11.40 

10.72 

10.31 

10. 0 

9.7s 

9.42 

9.10 

As  will  be  seen  from  the  table,  the  only  data  required  are  the 
guage  pressure  and  point  of  cut-off;  having  those  two  items 
given,  we  find  from  the  table  the  free  air  required  per  I.  H.  P., 
and  it  will  only  be  necessary  to  multiply  this  amount  by  the 
total  I.  H.  P.  of  the  motor  to  determine  the  total  quantity  of 
free  air  required  and  consequently  the  size  of  an  air  compressor 
to  furnish  the  air. 

These  figures  do  not  take  account  of  clearance,  but  it  will 
be  an  easy  matter  to  add  the  per  eent  of  clearance  after  having 
determined  the  total  amount  of  free  air  required. 

It  will  also  be  noticed  that  the  free  air  consumption  is  based 
upon  the  use  of  cold  air,  i.e.,  initial  temperature  of  air  at  60° 
F.  In  case  reheating  is  resorted  to  there  will  be  a  correspond- 
ing decrease  in  the  amount  used  depending  upon  the  tempera- 
ture of  air  at  admission  to  motor,  and  will  be  proportional  to 

T 
the  ratio  of  -^  where  T„  =460  -|-  60  =  520°  F.  absolute  tempera- 

ture  and  T„=  460  +  temperature  of  air  at  admission  to  motor. 


266  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

Thus  if  the  air  is  reheated  to  300°  F.,  the  quantity  in  the 

table  will  have  to  be  multiplied  by  %^ — ^t =  5-    _    gg^ 

460  +  300       760 

A  further  use  of  this  table  is  to  find  the  most  economical 

point  of  cut-off  for  gauge  pressures  from   30    pounds   to    150 

pounds  per  square  inch.     This  fact  is  apparent  from  a  study  of 

each  vertical  column;    thus,  at  60  pounds  pressure,  the  lowest 

consumption  of  free  air  per  I.  H.  P.  is  at  i  cut-off,  while  a  40 

pounds  pressure  will  work  most  economically  at  1^  cut-off. 

— F.  C.   Weber  in   "  Compressed  Air.'' 


METER    MEASUREMENT    OF    COMPRESSED   AIR. 

The  renting  of  air  power  caused  by  the  rapidly  extending  use 
of  compressed  air  requires,  for  measuring  the  quantity  used  by 
an  air  tenant,  a  means  that  is  reliable  within  a  small  fraction  of 
error.  The  measurement  of  water  power  is  well  established, 
but  the  measurement  of  steam  power,  except  by  the  indicator, 
is  but  little  practised  by  a  meter. 

The  needed  measurements  of  the  flow  of  natural  gas  to  con- 
sumers at  pressures  beyond  the  capacity  of  the  ordinary  gas 
meter  has  led  to  the  construction  of  a  meter  suitable  for  the 
measurement  of  the  flow  of  compressed  air  for  any  pressure  up 
to  500  pounds  per  square  inch.  The  Equitable  Meter  Com- 
pany, Pittsburg,  Pa.,  have  made  a  study  of  meters  for  com- 
pressed air  for  a  number  of  years  with  successful  results.  Their 
meters,  which  we  illustrate,  are  made  in  five  sizes  as  follows: 
10,  20,  30,  40,  and  50  thousand  cubic  feet  maximum  capacity 
per  hour. 

The  method  of  measurement  is  by  the  amount  of  air  in 
cubic  feet  at  the  pressure  at  which  it  passes  through  the  meter, 
no  matter  if  the  air  pressure  is  i  pound  or  100  pounds  to  the 
square  inch ;  and  then,  to  find  the  total  volume  of  free  air  passed, 
the  volume  of  compressed  air  will  have  to  be  reduced  into  a 
volume  of  free  air. 


MEASUREMENT    OF    COMPRESSED    AIR. 


267 


This  may  be  readily  done  by  multiplying  the  meter  index 
measurement  in  cubic  feet  by  the  ratio  of  isothermal  compres- 
sion in  column  3,  Table  XVII.,  in  this  work.  There  is  very 
little  friction  in  the  meter  mechanism,  amounting  to  only  about 
one  ounce  absorption  in  pressure  under  any  pressure  passing 
through  the  meter.     The  meter  is  also  provided  with  a  relief 


Fig.    79  —THE   AIR   METER. 

valve  to  guard  against  wreckage  of  the  meter  mechanism  by  a 
sudden  change  of  pressure  on  its  two  sides  by  accident. 

As  the  installation  of  compressed-air  central  plants  for  dis- 
tributing power  is  gaining  daily  in  importance,  the  problem  of 
measuring  the  amount  of  compressed  air  at  certain  pressures 
used  by  any  consumer  confronts  not  only  the  central  plant  own- 
ers, but  also  the  consumer.  The  consumer  should  know  how 
much  air  he  uses  in  order  to  know  that  he  is  charged  reason- 
ably for  it,  and  the  central  plant  owners  must  also  know  how 
much  every  consumer  uses  in  order  to  avoid  abuse  and  to  as- 
certain whether  the  plant  is  operated  on  a  paying  basis. 


268  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

Thus  the  central  plant  owners,  having  a  main  supply  pipe 
which  may  be  branched  off  for  distributing  to  mines  or  manu- 
facturing establishments,  will  find  the  necessity  of  installing 
meters  and  other  apparatus  which  cannot  be  tampered  with, 
and  which  at  the  end  of  each  month  will  be  able  to  give  not 
only  themselves,  but  also  the  consumer,  proper  data  from  which 
the  bills  for  the  month  can  be  figured. 

The  only  way  properly  to  determine  the  amount  of  com- 
pressed air  used  by  any  single  consumer  is  to  determine  the 
amount  of  free  air,  which,  if  multiplied  by  the  mean  average 
pressure,  will  give  the  total  amount  of  energy  furnished. 

The  next  question  of  importance  to  be  considered  is  for  both 
producer  and  consumer  to  know  that  the  air  pressure  is  as 
steady  as  possible,  and  sufficient  to  run  the  apparatus  to  be 
operated  by  compressed  air,  as  there  would  be  no  use  for  a 
consumer  to  pay  for  a  larger  volume  of  compressed  air  at  50 
pounds  pressure  should  he  require  80  pounds  pressure,  as  a 
large  quantity  of  air  at  a  low  pressure  would  not  do  his  work ; 
thus  it  would  be  necessary  to  install  a  compressed-air-pressure 
recording  gauge  in  connection  with  each  meter,  and  at  the  end 
of  the  month  the  mean  average  pressure  could  be  figured ;  and 
this,  multiplied  by  the  number  of  cubic  feet  of  free  air,  the 
product  representing  the  energy  furnished,  would  enable  both 
producer  and  consumer  to  settle  upon  the  amount  to  be  paid. 

The  problem  has  been  explained  clearly  enough,  but  it  may 
be  added,  however,  that  it  would  always  be  advisable  to  install 
a  small  receiver  next  to  the  meter,  and  that  the  pressure  record- 
ino-  gauge  should  be  connected  with  this  receiver;  this,  not 
only  to  avoid  vibration  of  the  recording  finger,  but  also  to  pre- 
vent any  shock  to  the  meter. 

It  should  be  noted  also  that  a  consumer  situated  far  away 
from  the  central  power  plant  should  pay  more  per  unit  of 
energy  than  one  near  by,  for  the  reason  that  the  friction  in 
long  pipes  amounts  to  a  certain  percentage  of  power,  and  that 
a  long  pipe  line  is  more  subject  to  leaks  and  requires  more  at- 
tention than  a  short  one. 


Chapter  XVIII. 


AIR   COMPRESSORS 


269 


AIR    COMPRESSORS. 

One  of  the  earliest  compressed-air  devices  was  the  trompe 
or  hydraulic  air  blast  for  forges.  Its  capacity  was  sufficient  for 
the  wants  of  the  times,  which  made  it  the  principal  means  for 
furnishing  a  steady  blast  for  the  Catalan  forges  of  the  early 


Fig.  So.— the  trompe. 


years  of  the  iron  age.  It  could  produce  a  pressure  from  an 
ounce  to  one  pound  or  more,  according  to  the  height  of  the 
water  shaft  and  the  depth  of  the  water  seal.  In  the  trompes  of 
the  best  construction  the  water  seal  was  a  sliding  gate  which 
could  be  operated  to  produce  any  desired  pressure  within  the 
range  of  the  apparatus.  Its  operation  was  as  follows  (Fig.  80) : 
the  falling  column  of  water  draws  in  air  through  the  small  in- 
clined orifices  as    shown    b}-  the    arrows,  carrying  it   into  the 


272 


COMPRESSED    AIR    AND    ITS    ATPLICATIONS. 


reservoir  where  it  separates,  and  is  discharged  through  the 
tuyere  pipe.  The  outlet  discharges  the  water  through  an  in- 
verted siphon,  carried  high  enough  to  balance  the  air  pressure. 
In  the  principles  of  the  trompe  is  found  a  correspondence 
and  suggestion  of  the  experiments  made  by  J.  P.    Frizell  in 


Fig.  8i.— the  frizell  system. 


1877,  and  since  carried  out  on  a  larger  scale  by  C.  H.  Taylor 
in  the  practical  hydraulic  air  compressors  at  Magog,  Quebec, 
and  at  Ainsworth,  B.  C. 

Many  experiments  have  been  made  to  compress  air  by  the 
direct  and  injector  system  for  small  quantities,  by  the  use  of 
water  under  pressure  from  city  water  supply. 

By  direct  pressure  it  requires  an  equal  quantity  of  water  to 
the  volume  of  free  air  compressed  to  nearly  the  same  pressure 
as  the  water.  By  the  injector  system,  the  only  available  ex- 
periments are  those  of  M.  Romally,  in  France,  who  found  that 
with  35  feet  head  only  46  per  cent  of  the  volume  of  the  water 
used  was  equal  to  the  volume  of  free  air  at  a  pressure  of  2 1 
pounds  per  square  inch ;  thiis  realizing  an  air  pressure  of  138 
per  cent  of  the  hydraulic  head  and  less  than  one-half  the  vol- 
ume, an  efficiency  of  about  63  per  cent. 

Mr.  Frizell's  experiments  involved  a  large  outlay  in  cost  of 
plant,  and  where  there  is  a  moderate  water-fall  and  plenty  of 
water  this  is  no  doubt  the  cheapest  working  method  of  com- 
pressing air.     The  general  idea  of  Mr.  Frizell  was  to  utilize  a 


AIR    COMPRESSORS. 


273 


high  water-fall  with  built-up  shafts  and  air  chamber,  or  with 
a  low  water-fall  to  sink  shafts  with  an  air-gathering  chamber 
at  the  bottom  and  air  pipe  leading  to  the  surface  as  shown  in 
Fig.  81.  The  entrance  at  A  in  the  cut  was  a  circular  hollow 
dam  with  a  conical  inlet.  The  annular  chamber  under  the  dam 
communicated  with  the  outer  air  and  was  perforated,  so  that  the 
falling  water  drew  down  the  air  and  by  its  velocity  carried  the 
air  to  the  receiving  chamber  below.  This  suggestion  and  ex- 
periments lay  in  abeyance  under  the  Frizell  patent  for  many 
years,  and  was  supplemented  by  a  similar  patent  to  Mr.  George 
Waring.  The  efhciency  in  Frizell's  early  experiments  was  26 
per  cent  of  the  fall  of  water  used  in  the  apparatus.  Later  im- 
provements by  him  raised  the 
efficiency  to  52  per  cent  with 
a  head  of  5  feet. 

The  hydraulic  compressor 
system  of  INIr.  Taylor  is  il- 
lustrated in  Figs.  82  and  83, 
in  which  a  large  number  of 
small  air  tubes  are  distributed 
around  an  annular  water  inlet 
to  the  down-flow  pipe.  One 
of  its  several  forms  of  con- 
struction is  shown  in  Fig.  82, 
and  more  fully  illustrated  in 
Figs.  84  and  85. 

A  number  of  air  tubes, 
c,  c,  terminate  at  the  conical 

entrance  of  the  down-flow  pipe,  B,  at  a,  a.  Fig.  82.  A  supply  of 
water  to  the  chamber  A,  A,  and  its  flow  down  the  pipe,  draws 
air  through  the  small  pipes,  carrying  it  down  to  the  separating 
tank,  c,  c,  where  it  is  liberated  at  the  pressure  due  to  the  hy- 
drostatic head.  The  air  is  delivered  through  a  pipe,  as  shown 
in  the  cut,  and  the  water  rises  through  a  pipe  or  open  shaft  to 
the  tail  race. 


Fig.  82.— the   taylor  hydraulic  air   com- 
pressor. 


2/4 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


The  compressor  as  erected  at  Magog,  Quebec,  gives  in  air 
power  62  per  cent  of  the  water  power  used  and  delivers  155 
horse  power  in  compressed  air  at  52  pounds  gauge  pressure. 


^^1^^^^^    P^^^^^SJ^^ 


Fig.  83.— hydraulic  air  compressor. 
Magog,  Quebec.     Air  head  section. 


A  most  remarkable  feature  of  this  system  is  that,  notwith- 
standing that  the  air  is  compressed  by  the  weight  of  the  water 
and  in  actual  contact  with  it,  the  air  so  compressed  is  delivered 


AIR    COMPRESSORS.  2/5 

in  the  receiver  and  thence  to  the  transmission  pipe  drier  than 
when  drawn  in  from  the  atmosphere. 

At  first  sight  this  would  seem  impossible,  but  it  is  well 
known  that  in  a  high  temperature  moisture  is  held  longer  in 
air  than  in  a  lower  temperature,  hence  the  contact  of  the  air 
globules  with  the  cold  water  keeps  down  the  temperature  usu- 
ally caused  by  the  compression  of  air,  and  the  atmospheric 
moisture  held  in  the  globules  condenses,  as  it  were,  on  the 
walls  of  these  globules,  and  at  the  point  of  separation  the  air 
and  water  are  absolutely  separated,  leaving  the  air  all  ready 
for  distribution  at  the  same  temperature  as  the  water  it  has 
just  left,  and  drier  than  when  first  taken  in  through  the  small 
air  pipes. 

Another  feature  is  that  the  power  of  the  water  can  be  con- 
verted into  compressed  air  at  any  pressure  per  square  inch, 
giving  the  same  efficiency  at  either  high  or  low  pressure  with  a 
far  less  loss  of  energy  than  by  any  other  process  of  transform- 
ing a  water  power  into  transmittable  force,  and  with  unvarying 
pressure. 

Should  the  volume  of  air  taken  down  be  greater  than  that 
being  used,  it  accumulates  in  the  receiver  until  it  forces  the 
water  below  the  lower  end  of  the  receiver,  and  the  surplus 
passes  up  with  the  return  water,  thereby  forming  a  perfectly 
automatic  safety-valve,  without  requiring  any  attendance  what- 
ever. It  will  be  observed  that  the  material  used  in  the  con- 
struction of  the  down -flow  pipe  need  only  be  of  sufficient 
strength  to  carry  the  weight  of  water  and  pressure  generated  in 
the  working  head  of  the  water  power,  as  once  it  reaches  the 
tail-race  level  the  internal  pressure  is  gradually  neutralized 
from  that  point  down  by  the  pressure  in  the  return  water  sur- 
rounding the  down-flow  pipe ;  so  that  any  pressure  almost  may 
be  reached  without  increasing  the  strength  of  the  down-flow 
pipe.  The  material  for  the  down-flow  pipe  ma}'  be  of  iron,  or 
wood  hooped  with  iron,  and  the  shaft  may  be  constructed  of 
the  cheapest  of  timber;    and  as  it  is  preserved  by  being  con- 


2/6 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


i  1-1  111' 


Sectional  View 
Fig.  84 —hydraulic  air  compressor. 
Magog,  Quebec.     Air  chamber  section. 


AIR   COMPRESSORS. 


277 


stantly  in  the  water,  there  is  practically  no  limit  to  its  dura- 
bility. 

By  this  system  low  falls,  otherwise  useless,  may  be  utilized, 
and  the  same  pressure  obtained  as  from  high  falls,  the  horse 
power  being  determined  by  the  diameter  of  the  down-flow  pipe, 
and  the  height  and  volume  of  water  in  the  fall,  while  the  press- 
ure depends  solely  upon  the  depth  of  the  well  or  shaft;  there- 
fore any  desired  pressure  can  be  obtained. 

In  the  apparatus  at  Magog,  Quebec,  the  receiver  is  suffi- 
ciently large  in  diameter  to  allow  the  air  to  rise  to  the  surface 

Plan  of  Head  Piece 


Fig.  85— plan  of  air  tubes. 


of  the  water  therein,  from  whence  it  is  taken  through  the  air 
pipe  for  transmission  to  be  utilized  as  power  or  for  other  pur- 
poses. The  water,  being  kept  down  by  the  pressure  of  the  air, 
is  forced  out  through  the  open  bottom  of  the  receiver  and  up 
the  shaft  around  the  down-flow  pipe  to  the  tail-race  level. 

The  compressor  is  so  constructed  as  to  permit  of  its  being 
regulated  to  furnish  any  proportion — from  one-third  of  its  ca- 
pacity— using  water  proportionately  with  a  like  efficiency. 

B}'  reference  to  the  head  section  (Fig.  83)  it  will  be  noticed 
that  the  head  piece  is  telescoped  into  the  down-flow  pipe,  and 
raised  or  lowered  by  means  of  a  hand-wheel  on  top,  thus  per- 
mitting the  flow  of  water  to  be  regulated,  or  to  lift  it  above  the 


2/8  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

water  level  and  stop  entirely  the  flow  of  air,  the  water  being 
regulated  by  the  head  gate. 

Briefly  stated,  the  air  is  compressed  by  the  direct  pressure 
of  falling  water  without  the  aid  of  any  moving  machinery,  and 
practically  without  expense  for  maintenance  or  attendance  after 
installation. 

By  this  system  any  fall  of  water  varying  in  working  head 
may  be  utilized,  and  any  pressure  required  can  be  produced 
and  uniformly  maintained  up  to  the  capacity  of  the  water 
power,  delivering  the  compressed  air  at  the  temperature  of  the 
water,  and  in  a  drier  state  than  is  possible  by  any  known  means 
of  compression,  thereby  avoiding  all  loss  by  condensation  or 
shrinkage  by  cooling  of  the  air  after  compression. 

The  water  may  be  conveyed  to  the  compressor  by  means  of 
an  open  flume;  or,  as  shown  in  the  diagram,  through  a  pipe 
supplying  a  tank  or  stand-pipe  around  the  headpiece  of  the 
compressor,  where  it  can  attain  the  same  level  as  the  water  in 
the  dam  or  source  of  supply. 

Around  the  head-piece  are  placed  a  large  number  of  small, 
horizontal  air  pipes,  drawing  their  supply  of  air  through  larger 
vertical  pipes,  which  extend  above  the  surface  of  the  water  and 
open  to  the  atmosphere. 

As  the  water  enters  the  down-flow  pipe  and  passes  the  ends 
of  these  small  air  pipes,  it  draws  in  the  air  in  the  form  of  small 
uniform  globules,  which,  becoming  entangled  in  the  descending 
water,  are  carried  down  to  the  receiver  at  the  bottom  of  the 
pipe,  compressing  the  air  by  the  pressure  of  the  water  sur- 
rounding these  globules  until  they  reach  the  point  of  separa- 
tion. This  pressure  is  maintained  so  long  as  there  remains 
any  air  in  the  receiver  chamber. 

The  enlargement  of  the  down-flow  pipe  at  the  bottom  sec- 
tion was  made  to  lessen  the  velocity  of  the  water  and  air  at  that 
point,  which  was  found  to  facilitate  the  separation  of  the  air 
from  the  water  by  coalescing  the  small  globules  of  air  and  the 
better  separation  at  the  deflecting  plate  below.      The  deflecting 


AIR    COMPRESSORS. 


279 


plate  prevents  the  plunge  of  the  down-flowing  water  into  the 
separating  part  of  the  tank  and  by  its  deflections  gives  the  air  a 
more  ready  separation  from  the  water.  By  this  arrangement 
no  air  was  found  in  the  water  discharge  pipe. 

In  tests  of  efficiency  it  has  been  found  that  the  gross  power 
of  the  water  passing  through  the  compressor  due  to  its  natural 
fall  was  158  horse  power,  of  which  1 1 1  horse 
power  was  utilized  in  the  work  of  air  com- 
pression, giving  an  efficiency  of  70  per  cent 
of  the  gross  power  used. 

Later  experiments  indicate  that  an  effi- 
ciency of  75  per 
cent  may  be  ob- 
t  a  i  n  e  d  by  a 
modification  of 
the  air  inlet    pipes    and    water  head. 

In  Fig.  86  is  illustrated  the  Taylor 
hydraulic  air-compressing  plant  at 
Ainsworth,  B.  C,  which  was  estab- 
lished in  a  trussed  tower  in  order  to 
carry  up  the  air  head  to  a  level  with 
the  flume,  of  which  Fig.  86  represents 
the  elevation  and  arrangement  of  the 
head.  The  available  working  head 
from  the  water  level  in  the  head  stock 
to  the  tail  race  is  102  feet;  the  depth 
of  the  shaft  is  210  feet,  and  the  depth 
of  the  air  chamber  at  the  bottom  of 
the  shaft  is  17  feet,  from  which  the 
water  closure  of  the  down-flow  tube 
leaves  200  feet  as  the  available  hydro- 
static pressure,  which  gives  an  air  pressure  of  87  pounds  per 
square  inch.  The  flume  supplying  water  from  Coffee  Creek, 
1,350  feet  distant,  is  5  feet  in  diameter,  of  stave-barrel  construc- 
tion.    The  tower  head   is  also  of  wood  staves,   is    12    feet   in 


Fig.   86.-Hvr>RUALic    air    com- 
pressor. 

Ainsworth,  B.  C. 


28o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


diameter  and  20  feet  high.  The  down-flow  pipe  is  of  the  same 
construction,  2  feet  9  inches  in  diameter,  widening  slightly 
at  the  bottom  to  retard  the  velocity  of  the  descending  water 
and  allow  it  to  impinge  upon  a  whorling  cone  that  produces  a 
circling  current  in  the  air  chamber  that  facilitates  the  separa- 
tion of  the  compressed  air  from  the  water.  The  air  rinses  to  the 
top  of  the  separating  chamber  and  is  delivered  through  a  9-inch 
pipe  to  the  various  branches  for  air  distribution  at  the  ground 
surface.  A  secondary  pipe  is  carried  from  midway  in  the  sepa- 
rating chamber  to  the  surface  above  the  tail  race  that  seals  the 
air  space  with  water  when  the  air  is  being  used  in  excess  of 


Fig.    87.— HARTFORD  AIR   COMPRESSOR. 


compression,  and  allows  the  air  to  escape  when  it  accumulates 
and  pushes  the  water  surface  below  the  mouth  of  the  air  pipe ; 
thus  making  an  air-pressure  regulator  within  the  limit  of  one- 
pound  air  pressure. 

The  regulation  of  the  air-inlet  pipes,  of  which  there  are 
about  three  thousand  tubes,  f-inch  diameter  and  the  conical 
adjutage,  is  made  by  raising  or  lowering  the  air  pipes  and  cone 
by  a  screw  and  wheel,  as  shown  in  Fig.  86.  The  velocity  of 
the  water  in  the  down-flow  pipe  is  about  34  feet  per  second, 
and  the  velocity  of  the  indraft  of  air  is  nearly  the  same.  The 
air  is  received  by  the  water  in  millions  of  globules,  which  in  a 
great  measure  retain  their  individuality,  gradually  becoming 
smaller  by  the  increasing  water  pressure  until  they  are  liber- 
ated in  the  air  chamber  below. 

The  air  intake  is  estimated  at  5,000  cubic  feet  of  free  air 


AIR    COMPRESSORS. 


281 


per  minute,  and  at  85  pounds  pressure  should  develop  nearly 
500  horse  power. 

The  air  plant  has  a  distributing  system  of  over  11,000  feet 
of  pipe  of  varying  sizes  in  use  in  a  number  of  mines.  The  air 
is  unusually  dry,  and  the  drills  and  hoists  have  no  trouble  from 
frosted  exhausts. 

The  hydraulic  air  compressor  of  the  L.  E.  Rhodes  Com- 
pany, Hartford,  Conn.  (Fig.  87),  consists  of  two  displacement 
cylinders  with  alternating  water 
valves  to  control  the  operation  of  the 
compressor.  It  operates  by  water 
pressure  from  any  water-works  sup- 
ply, and  will  compress  an  equal  vol- 
ume of  free  air  to  the  volume  of 
water  used,  to  nearly  the  same  press- 
ure as  the  water  supply.  It  is  a 
most  convenient  apparatus  for  sup- 
plying compressed  air  for  dental  air 
tools,  spraying,  and  for  man)'  uses 
where  a  small  quantity  of  compressed 
air  is  required  in  experimental  and 
laboratory  work.  In  Fig.  88  is  illus- 
trated the  vertical  differential  com- 
pressor, in  which  a  larger  volume  of  air,  in  proportion  to  the 
water  used,  is  obtained  at  lower  pressure  than  that  of  the  water 
by  the  differential  area  of  the  pistons. 

A  direct-acting  hydraulic  air  compressor  was  used  at  the 
Mont  Cenis  tunnel,  using  a  mountain  stream  giving  a  head  of 
85  feet.  A  number  of  compressors  were  installed  on  this  prin- 
ciple by  vSommeiller,  which  gave  satisfactory  results  at  that 
time,  owing  to  the  favorable  location  of  the  mountain  stream. 
This  idea  has  been  followed  since  by  man}^  patents  on  direct- 
acting  hydraulic  air  compressors.  The  want  of  favorable  loca- 
tions where  high  pressure  and  volume  can  be  obtained  has  caused 
this  system  to  be  neglected. 


Fig 


.—VERTICAL  COMPRESSOR. 


282 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig. 


-DARLINGTON   COMPRESSOR. 


This  was  followed  by  the  Darlington  hydraulic  piston  com- 
pressor, illustrated  in  Fig.  89,  which  was  designed  somewhat 
after  the  model  of  the  Sommeiller,  using  water  for  a  piston, 

which  was  operated  by  a  piston  driven 
by  a  steam  engine.  It  was  much  in 
use  in  France,  Germany,  and  Belgium 
during  the  earlier  period  of  air  com- 
pression for  practical  work, 
but  was  soon  superseded  by 
the  modern  designs.  Its 
action  was  as  follows:  A 
reciprocating  piston  in  the 
water  cylinder,  G,  produces  an  oscillating  motion  in  the  water 
of  the  two  vertical  cylinders,  drawing  in  air  through  the  flap 
valves  at  the  side,  and  discharging  the  compressed  air  through 
the  valves  at  the  top.  The  water  pipes,  /,  /,  /,  are  to  supply 
the  place  of  water  ejected  through  the  air  valve  by  delivering 
all  the  air  compressed  at  each  stroke  of  the  piston. 

A  further  advance  in  air-compressor  design  seems  to  have 
been  made  in  the  model  of  the  Dubois  and  Fran9ois  compres- 
sors, which  was  intended  to  improve  on  the  slow  work  of  the 
Sommeiller  compressors  by  charging  the  cylinder  with  no 
more  water  than  would  fill  the  valve  chambers,  and  inserting 
water  jets  for  cooling  the  air  dur- 
ing compression,  and  to  supply 
the  waste  by  carrying  part  of 
the  water  through  the  exit 
valves. 

In  this  design  the  practical 
operation  and  speed  seemed  a 
great  advance  over  the  former 
designs,  and  for  a  time  seemed 

to  take  a  leading  place  for  air  compression  in  France  and  Ger- 
many. 

In  the  mean  time  progress  was  being  made  in  England  and 


Fig.      go.— DUBOIS     AND       FRANCOIS     COM 
PRESSOR. 


AIR    COMPRESSORS. 


283 


the  United  States  by  reducing  the  cylinder  clearance,  and  with 
only  a  small  spray  for  cooling  effect  and  for  balancing  the  un- 
equal effect  of  the  steam  impulse  and 
the  air  resistance,  when  steam  was 
used  expansively  and  for  its  best 
economy.  The  first  efforts  were  by 
placing  the  steam  and  air  cylinder 
at  a  right  angle  and  operating 
through  angular  cranks.  This  ar- 
rangement used  in  the  Burleigh 
and  early  Ingersoll  type  is  sketched 
in  Fig.  91,  in  which  the  cylinders 
were  set  at  90°  and  the  cranks  at  30^ 


Fig.  91.— type. 


Ran  a  8r 
\Yc\x\nj 


Fig.  92.— type. 


Ths  plan  was  also  used 
by  Delavergne  for  ammonia  com- 
pressors, and  is  still  in  use  by  the 
Frick  Company  and  others  for  am- 
monia. 

Another  form  of  construction  by 
Rand  and  Waring  was  in  use  in 
1872,  and  is  shown  in  sketch  (Fig. 
92).  The  steam  cylinder  was 
placed  over  the  air  cylinders  at  an 
angle  of  45°,  and  connected  to  a  single  crank.  This  form  made 
a  fairly  compact  arrangement  of  frame,  and  in  a  measure 
equalized  the  steam  and  air 
pressures.  Davies  in  Eng- 
land also  worked  on  these 
ideas  and  built  compressors 
with  cylinders  at  an  angle  of 
135''  and  connected  to  a  single 
crank  (Fig.  93).  It  was 
early  perceived  that  an  angu- 
lar position  of  the  cylinders 

involved  expensive  construction  and  unsteadiness,  and  later  ex- 
perience  has  proved  that  it  is  expensive  in  construction  and 


r^ 


T 


Fig.  93.— type. 


284 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


does  not  fully  equalize  the  compression  strains.  This  form  of 
construction  involves  much  greater  weight  and  strength  in  the 
frame,  all  of  which  has  been  obviated  in  the  later  construction 
of  straight-line  compressors  with  the  controlling  power  in  a 
heavy  fly-wheel  and  moving  parts. 

Many  efforts  were  made  to  equalize  the  power  and  resistance 
by  constructing  the  air  compressor  on  the  crank-angle  princi- 

Prirv-cipVc     or    \>iTett     Con-v.ipxe.'b'av.ow 


.>—;/   > 


ate  atru 


Fig.  94.— direct  compression. 


pie,  putting  the  cranks  at  various  angles,  and  by  direct-line 
positions  of  steam  and  air  cylinders,  and  this  is  yet  in  practice 
for  compressors  in  ammonia  refrigerating  apparatus. 

Fig.  94  shows  the  true  relation  of  pressures  when  the  steam 
and  air  pistons  are  on  a  direct  or  straight-line  piston  rod. 

It  is  evident  that  an  air  compressor  which  has  the  steam 
cylinder  and  the  air  cylinder  on  a  single  straight  rod  will  apply 
the  power  in  the  most  direct  manner,  and  will  involve  the  sim- 
plest mechanics  in  the  construction  of  its  parts.  It  is  evident, 
however,  that  this  straight-line,  or  direct,  construction  results 
in  an  engine  which  has  the  greatest  power  at  a  time  v\'hen  there 
is  no  work  to  perform.  At  the  beginning  of  the  stroke,  steam 
at  the  boiler  pressure  is  admitted  behind  the  piston;  and  as  the 
air  piston  at  that  time  is  also  at  the  initial  point  in  the  stroke, 
it  has  only  free  air  against  it.  The  two  pistons  move  simulta- 
neously, and  the  resistance  in  the  air  cylinder  rapidly  increases 
as  the  air  is  compressed.  To  get  economical  results  it  is,  of 
course,  necessary  to  cut  off  in  the  steam  cylinder,  so  that  at  the 
end  of  the  stroke,  when  the  steam  pressure  is  low,  as  indicated 


AIR    COMPRESSORS. 


285 


by  the  dotted  line  (Fig.  94),  the  air  pressure  shall  be  high,  as 
similarly  indicated.  The  early  direct-acting  compressor  used 
steam  at  full  pressure  throughout  the  stroke.  The  Westing- 
house  pump,  applied  to  locomotives,  is  built  on  this  principle, 
and  those  who  have  observed  it  at  work  have  perhaps  noticed  that 
its  speed  of  stroke  is  not  uniform,  but  that  it  moves  rapidly  at 
the  beginning,  gradually  reducing  its  speed,  and  seems  to  labor 
until  the  direction  of  stroke  is  reversed.  Such  construction  is 
admitted  to  be  wasteful,  but  in  some  cases,  notably  that  of  the 
Westinghouse  pump,  economy  in  steam  consumption  is  sacri- 
ficed to  lightness  and  economy  of  space. 

The  alternating  pressures  in  a  steam-driven  compressor 
with  a  single  air  and  steam  cylinder  are  largely  overcome  in 
a  duplex  compressor,  as  shown  by  the  two  positions  of  the 
steam  and  air  pistons  in  the  upper  section  of  the  cut  (Fig.  95), 
when  moving  in  the  same  direction  as  shown  by  the  direction 
of  the  two  cranks  at  right  angles  on  the  shaft,  and  when  the 


Fig.  95.— action  of  the  duplex  air  compressor. 


pistons  are  moving  in  opposite  directions  as  shown  by  the  posi- 
tion of  the  cranks  in  the  lower  section  of  the  cut. 

The  conditions  of  equalization  of  pressures  are  shown  by 
commencing  at  that  point  of  the  stroke  indicated  in  the  top  sec- 
tion. The  upper  right-hand  steam  cylinder,  having  steam  at 
full  pressure  behind  its  piston,  is  doing  work  through  the  angle 
of  the  crank  shaft  upon  the  air  in  the  lower  left-hand  cylinder. 
At  this  point  of  the  stroke  the  opposite  steam  cylinder  has  a 


286 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


reduced  steam  pressure  and  is  doing  little  or  no  work,  because 
the  opposite  air  cylinder  is  beginning  its  stroke.  Referring 
now  to  the  lower  section,  it  will  be  seen  that  the  conditions  are 
reversed.  One  crank  has  turned  the  centre,  and  that  piston 
which  in  the  upper  section  was  doing  the  greatest  work  is  now 
doing  little  or  nothing,  while  the  labor  of  the  engine  has  been 
transferred  to  those  cylinders  which  a  moment  before  had  been 
doing  no  work. 

There  are  some  advantages  in  the  duplex  construction,  and 
some  disadvantages.  The  crank  shafts  being  set  quartering, 
as  is  the  usual  construction,  the  engine  may  be  run  at  low 
speed  without  getting  on  the  centre.  Each  half  being  com- 
plete in  itself,  it  is  possible  to  detach  the  one  when  only  half 
the    capacity   is    required.     The    power   and    resistance   being 


Fig.  96.— dikect  acting. 

equalized  through  opposite  cylinders,  large  fly-wheels  are  not 
necessary.  Strange  to  say,  the  American  practice  seems  to  be 
to  attach  enormous  fly-wheels  to  duplex  air  compressors.  It  is 
difficult  to  justify  this  apparently  useless  expense  in  view  of 
the  facts  shown  in  Fig.  95.  A  fly-w^heel  does  not  furnish 
power,  nor  does  it  add  to  the  economy  of  an  engine  except  in 
so  far  as  it  enables  it  to  cut  off  early  in  the  stroke,  and  to 
equalize  the  power  and  resistance.  In  other  words,  a  fly-wheel 
is  not  a  source  of  power,  and  in  many  cases  it  is  only  a  means 
by  which  is  accomplished  equal  rotative  speed.  It  takes  power 
to  move  matter,  and,  assuming  that  other  conditions  are  equal, 
every  engine  that  carries  a  fly-wheel  that  is  larger  than  is 
necessary  consumes  a  certain  number  of  foot-pounds  in  turn- 
ing so  much  metal  around  through  space.  Were  it  possible  to 
cut  off  at  the  same  point  and  rotate  as  positively  without  a  fly- 


AIR    COMPRESSORS.  2  8/ 

wheel,  it  would  be  done  away  with  entirely.  Some  straight- 
line  air  compressors  are  so  constructed  that  the  momentum  of 
the  piston  and  other  moving  parts  is  nearly  sufficient  to  equal- 
ize the  strains  without  a  fly-wheel ;    but  the  fly-wheel  is  there 


Fig.  97.— straight  line. 

because  it  insures  a  definite  length  of  stroke,  and  because  it 
enables  us  to  operate  eccentrics  and  to  regulate  the  speed  of  the 
engine  uniforml}'. 

Objections  to  the  duplex  construction  are :  The  strains  are 
indirect,  angular,  and  intermittent.  It  is  necessary  therefore 
to  largely  increase  the  strength  of  parts ;  to  add  a  crank  shaft 
of  larger  diameter  with  enormous  bearings,  and  to  build  ex- 
pensive and  very  secure  foundations.  Should  the  foundations 
settle  at  any  point,  excessive  strains  will  be  brought  upon  the 
bearings,  resulting  in  friction  and  liability  to  breakage.  A 
steam  engine  meets  with  a  resistance  on  its  crank  shaft  that  is 


Fig.  9S. -.\ik-brake  compressor. 


comparatively  uniform  throughout  the  stroke,  while  an  aii 
compressor  is  subject  to  a  heavy  maximum  strain  at  the  end 
of  the  stroke ;  hence  the  importance  of  direct  straight-line  con- 
nection between  power  and  resistance. 


288 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


The  friction  loss  on  a  duplex  compressor  seldom  gets  lower 
than  15  per  cent,  while  straight-line  compressors  show  as  low 
a  loss  as  5  per  cent. 

To  illustrate  the  leading  types  of  the  modern  direct-acting 
compressors,   the  follow^ing    sketch   cuts  are  representative  of 

some  of  the  leading  models: 

Fig.  96  is  an  elevation  of 
the    Clayton    air   compressor 
with  a  yoke-frame  connecting 
rod  in   line  with   the    piston 
rods,  the  crank  and  connect- 
ing    rod    operating  between 
the  rods  of  the  yoke  frame. 
Fig.     97    represents     the 
outline  of  the  "  Bennett  "  straight-line  compressor,  showing  a 
lever  valve  gear,  operated  by  direct  connection  from  the  lever 
to  the  eccentric  by  a  link. 

In  Fig.  98  is  represented  a  vertical  section  of  a  unique 
construction  in  air  compressors  in  which  a  double-acting  steam 
cylinder  operates  two  single-acting  air  cylinders  through  the 
medium   of  toggle   beams,    each   beam   having  two  stationary 


Fig.  99.— the  norwalk. 


Fig.  100.— tandem  cokliss. 


pivots  and  being  linked  to  the  beam  for  producing  parallel  mo- 
tion of  the  piston  rods  {New  York  Air  Brake  Company  model). 
In  Fig.  99  is  given  a  sketch  of  a  compound  straight-line 
steam-actuated  air  compressor  with  an  intercooler  connecting 
the  low-  and  high-pressure  cylinders  (type  of  the  Norwalk  Iron 
Works). 


AIR   COMPRESSORS. 


289 


The  attachment  of  the  air  cylinder  tandem  to  a  Corliss  en- 
gine is  one  of  the  improvements  of  late  years  in  the  line  of 
economy,  and  for  large  outputs  of  compressed  air  has  no  equal 
in  operative  duty. 

In  Fig.  100  is  illustrated  a  vertical  sketch  of  a  single  Corliss 
tandem-operated  air  compressor,  and  in  Fig.  loi  a  duplex  com- 
pressor of  the  slide-valve  gear  pattern  in  plan  and  elevation 
(the  piston  inlet  type  of  the  Ingersoll-Sergeant  Drill  Company). 


Fig.  ioi.— duplex  compressor. 


In  Fig.  102  is  a  sketch  illustration  of  a  straight-line  piston 
inlet  compressor  in  vertical  section  and  plan,  as  operated  by  a 
Pelton  water-wheel  (type  of  the  Ingersoll-Sergeant  Drill  Com- 
pany, which  will  be  described  in  detail  further  on). 

In  Fig.  103  is  represented  a  detailed  section  of  the  cylinders 
of  a  high-pressure  air  or  gas  compressor  of  the  Ingersoll-Ser- 
geant Drill  Company,  in  which  both  pistons  are  single-acting, 
with  water- jacketed  cylinders.  The  forward  motion  of  the 
pistons    allows   the   air    entering  at    the    port  A   to   be  drawn 

through  the  annular  valve  in  the  large  piston  to  be  compressed 
19 


290 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


by  the  back  stroke,   and  transmitted  to  the  compression  side 
of  the  high-pressure  piston  through  a  direct  outside  pipe  or 


Fig.  102.— pelton  wheel  compressor. 


through  an  intercooler.  The  lettered  parts  are  plainly  recog- 
nized and  need  no  special  explanation.  The  initial  air  cylinder 
is  made  of  a  size  to  meet  the  requirement  of  full  volume  to  the 
high-pressure  cylinder  and  to  equalize  the  machine  strains  due 


Fig.  103.— section  of  the  compound  air  cylinder. 


to  both  half-strokes,  or  one  revolution  of  the  fly-wheel.  The 
single-acting  principle  is  conducive  to  efficiency  in  jacket 
cooling. 


Chapter  XIX. 


AIR  COMPRESSORS— Continued 


AIR    COMPRESSORS. 

{Conti lilted.) 
AIR   COMPRESSORS    OF   THE    INGERSOLL-SERCIEANT   TYPE. 

The  early  compressors  of  the  Ingersoll-Sergeant  Drill  Com- 
pany were  made  with  solid  pistons  and  inlet  and  exit  valves  in 
the  heads  of  the  cylinders.  Gradual  improvements  in  their 
long  experience  have  led  to  higher  development  in  the  economy 
of  air  compression.  The  Meyer  variable  cut-off  and  the  air 
pressure  controlling  device  applied  to  the  steam  cylinder,  with 
a  large  reduction  in  the  clearance  of  the  steam  cylinder,  to- 
gether with  the  straight-line  effect,  have  brought  the  steam  end 
of  the  compressor  to  a  perfect  action.  Improvements  in  the 
air  cylinder  have  kept  even  pace,  and  among  them  we  illustrate 
the  piston  inlet  air  cylinder  (Fig.  105),  and  the  annular  valve 
at  G  in  the  cut.  The  air  is  taken  in  through  a  hollow  piston 
rod  at  R  and  into  the  hollovv^  piston,  and  delivered  to  the  cylin- 
der each  way  through  an  annular  steel  valve  that  opens  and 
closes  automatically  by  its  own  momentum  derived  from  the 
motion  of  the  traversing  piston  ;  requiring  no  springs  to  control 
its  operation.  It  has  a  large  area  of  opening  with  but  a  small 
throw  of  valve,  thus  quickly  opening  a  large  supply  port,  en- 
abling the  compressor  to  run  at  high  speed  without  a  reduction 
in  efficiency  and  with  safety  to  the  moving  parts.  As  the  travel 
of  the  valve  is  only  about  one-quarter  of  an  inch,  it  does  not 
move  far  enough  to  acquire  sufficient  momentum  to  injure 
itself  or  its  seat,  and  remains  perfectly  tight  till  worn  out.  It 
is  as  positive  in  its  action  and  as  indestructible  as  a  piston  ring. 
The  discharge  valves  are  of  the  cylindrical  poppet  type,  sliding 


294 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


AIR   COMPRESSORS    OF   THE    INGERSOLL-SERGEANT   TYPE.       295 


Fig.  105. —the  piston  inlet. 


in  screw  caps  with  helical  springs.     Cylinder    and  heads  are 
water-jacketed. 

In  Fig.  106  is  illustrated  a  late  improvement  in  the  valve 
arrangement  of  the  air  cylinders  of  this  company.  The  intake 
valves  are  made  large  and  of  light  weight,  and  so  protected  by 
the  overlap  of  the  cylin- 
der heads  that  they  can- 
not be  drawn  into  the 
cylinder  by  the  breakage 
of  a  stem.  The  vertical 
movement  of  all  the  air 
valves  insures  even  wear 
on  their  seats.  This  po- 
sition of  the  valves  enables  a  full  water-jacketing  of  the  heads 
of  the  cylinders. 

In  Fig.  107  is  illustrated  an  elevation  and  plan  of  the  piston- 
inlet  belt  compressor  of  this  company,  showing  the  swivel-block 
cross-head  for  equalizing  any  irregularity  in  setting  up  the 
connecting-rod  brasses,  a  special  feature  of  the  transmitting 
gear  of  these  compressors. 

In  Fig.  108  is  illustrated  the  unloading  device  by  which  a 
uniform  air  pres.sure  is  kept  in  the  receiver  and  pipe  line.  It 
is  automatic,  requiring  no  attention  from  the  engineer  further 
^__^  than   to  set  it  for  the    re- 


quired pressure.  A 
weighted  piston  safety- 
valve  is  attached  to  the  air 
cylinder,  and  connected 
with  the  air  receiver,  and 
with  a  discharge  valve  on 
each  end  of  the  air  cylin- 
der, also  with  a  balanced 
throttle  valve  in  the  steam 
pipe.  When  the  pressure  of  the  air  gets  above  the  desired 
point  in  the  receiver,  the  valve  is  lifted  and  the  air  is  exhausted 


Fig.  106  —vertical  v.^lve  cylinder. 


296 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


from  behind  the  discharge  valves,  thus  letting-  the  compressed 
air  at  full  receiver  pressure  into  the  cylinder  at  both  ends,  and 
balancing  the  engine.  At  the  same  instant  the  compressed 
air  is  exhausted  from  the  piston  connected  with  the  balanced 
steam  valve  and  the  steam  is  automatically  throttled,  so  that 
only  enough  steam  is  admitted  to  keep  the  engine  turning 
around,  or  to  overcome  the  friction,  no  work  being  done. 

When  the  compressor  is  unloaded,   it  is  evident  that  the 
function  of  the  air  piston  is  merely  to  force  the  compressed  air 


Fig.  107— the  piston  inlet  belt  compressor. 


through  the  discharge  valves  and  passages  from  one  end  to  the 
other  until  more  compressed  air  is  required,  this  being  indi- 
cated by  a  fall  in  the  receiver  pressure.  The  weighted  valve 
now  closes  and  the  small  connecting  pipes  are  instantly  filled 
with  compressed  air;  the  steam  valve  automatically  opens  and 
the  compression  goes  on  in  the  regular  way.  The  unloaded  in- 
dicator card  (Fig.  109)  shows  the  air-pressure  conditions  under 
the  control  of  the  unloading  device  by  the  black  lines,  and  the 
normal  compression  by  the  dotted  lines.  Another  function 
of  this  device  is  to  prevent  the  compressor  from  stopping  or 


AIR    COMPRESSORS    OF   THE    INCiERSOLL-SERGEANT   TYPE.       297 

getting  on    the   centre.     Direct-acting  compressors  are    liable 
to  centre  when  doing  work  at  slow  speed. 

In  Fig.  I  10  is  illustrated  a  pair  of  straight-line  air  compres- 
sors placed  side  by  side  as  a  duplex  compressor,  operated  from 
a  high  water-head  with  double  nozzles  and  Pelton  wheels.     The 


size  of  the  Pelton  wheels  for  direct  action  upon  the  air  pistons 
is  made  to  meet  the  requirement  of  a  half  speed  for  spouting 
velocity  of  the  water  at  the  nozzles  to  correspond  to  the  re- 
quired speed  of  the  compressor.  This  plant  was  sectionalized 
for  transport  on  mule-back,  and  operated  in  Peru,  South 
America. 


298 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


rry Air 

^y^     PfCSSU 

„..—'  line 


Atmospheric  line 


Fig.    109  — INUICATOK    CAKD  OF  THE   UNLOADED   AD<    CVLINDEK. 


AIR   COMPRESSORS   OF   THE   INGERSOLL-SERGEANT   TYPE.       299 


~      c 


300 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig. 


-DUPLEX  STEAM   DRIVEN    AND  COMPOUND  AIR   CYLINDER  COMPRESSOR    WITH  INTER- 
COOLER   IN  BASE. 


AIR    COMPRESSORS    OF   THE    INGERSOLL-SERGEAXT    TYPE.       3OI 


302 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


<       o 


c      p 


AIR    COMPRESSORS    OF    THE    INGERSOLL-SERGEANT    TYPE.       303 


Fig.  115.- battery  of  duplex  corliss  air  compressors. 
Corliss  type  of  air  valves  with  positive  motion. 


304 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


P'^u'TTT^r^ 


Fig.  ii6.— fouk-stage  air  compkessor. 

Twelfth  Avenue  and  Twenty-fourth  Street,  New  York  City,  Metropolitan  Street  Railway 

Company. 


AIR   COMPRESSORS    OF   THE    INGERSOLL-SERGEANT   TYPE.       305 


A    THOUSAND-HORSE-POWER    AIR    COMPRESSOR. 

The  four-stage  air  compressor  of  the  Ingersoll-Serg-eant 
Drill  Company  that  gives  power  to  the  cars  of  the  Metropolitan 
Street  Railway  Company  of  New  York  is  probably  the  largest 


'^0:i^$M^§^m?^^^^^^^^^ 


Fig.  117.  —the  vertical  high-pressure  four-stage  air  compressor. 
Front  view. 


air  compressor  yet  made  in  any  country,  and  embodies  charac- 
teristics in  design  and  construction  far  in  advance  of  ordinary 
practice. 

The  steam  power  of  the  compressor  consists  of  a  duplex 
vertical  cross  compound  engine  built  by  the  E.  P.  Allis  Com- 
pany,   Milwaukee,    Wis.,    having   cylinders   32   and   68   inches 


^o6 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


diameter  by  60  inches  stroke,  provided  with  Reynolds-Corliss 
valve  gear.  With  steam  pressure  of  150  pounds  and  40  revolu- 
tions per  minute,  it  is  equal  to  1,000  hor.se  power.  The  fly- 
wheel is  22  feet  in 
diameter,  and  weighs 
60  tons.  The  engine 
is  mounted  upon 
brick  piers,  and  di- 
rectly beneath  each 
s  t  e  a  m  cylinder  is 
placed  a  pair  of  air 
cylinders,  tandem, 
and  connected  to  the 
steam  cylinder  cross- 
heads  by  a  yoke 
frame.  The  low- 
pressure  air  cylinder 
and  first  interme- 
diate are  46  and  24 
inches  diameter 
placed  tandem ;  sec- 
ond intermediate  and 
high-pressure  cylin- 
ders are  14  and  6 
p.  1    .  inches    diameter    re- 

Knd  view. 

spectively,  also  tan- 
dem, and  the  stroke  the  .same  as  the  engine,  60  inches.  All  the 
air  cylinders  are  single-acting. 

The  free-air  capacity  per  revolution  is  56.73  cubic  feet;  ca- 
pacity at  40  revolutions  2,269  ^ubic  feet,  and  the  free-air  capac- 
ity at  60  revolutions  is  3,404  cubic  feet.  The  approximate 
pressure  in  the  first  cooler  is  40  pounds,  the  second  180  pounds, 
and  in  the  third  850  pounds,  the  final  approximate  pressure  in 
the  after-cooler  being  2,300  pounds. 

The  compressor  pistons  are  arranged  in  pairs  vertically  in 


-^v^'.p.-r^Ji, 


-"ss'Sa-i^'f 


,J:i:..,.\-.Y, 

Fig    lib.— four-stage  high-pressure  air  compressor. 


AIR    COMPRESSORS    OP    THE    INGERSOLL-SERGEANT    TVl'E.       307 


line  beneath  the  steam  cylinders,  the  initial  and  first  interme- 
diate air  cylinder  being  below  the  low-pressure  steam  cylinder, 
while  the  second  intermediate  and  high-pressure  air  cylinders 
are  below  the  high-pressure  steam  cylinder.  Motion  is  trans- 
mitted from  the  steam-engine  cross-heads  through  distance  rods 
for  each  cross-head  to  a  cross-head  attached  to  the  air- cylinder 
piston  rods. 

The  inlet  and  discharge  valves  of  the  initial  air  cylinder  are 
of  the  "  Mechanical  "  type  and  of  a  special  design.  Air  is  ad- 
mitted to  the  top  of  this  cylinder  through  a  supply  pipe  and 
leaves  the  cylinder  through  a  pipe,  by  which  it  is  conducted  to 
the  first  intercooler. 
From  the  cooler  the 
air  flows  through  a 
pipe  to  the  lower  end 
of  the  first  interme- 
diate air  cylinder, 
from  which  it  passes 
through  a  pipe  to  the 
second  intercooler. 
From  here  it  passes 
through  a  pipe  to 
the  upper  end  of  the 
second  intermediate 
cylinder,  from  which 
it  passes  to  the  third 
cooler,  and  from  here 
through  a  pipe  to 
the  lower  end  of  the 
high-pressure  cylin- 
der, and  from  this 
through  a  pipe  to  the  final  aftercooler,  from  which  it  is  led 
through  the  outlet  to  the  storage  bottles.  From  this  it  will  be 
seen  that  the  air  passes  through  the  upper  end  of  the  low- 
pressure  cylinder,  lower  end  of  the  first  intermediate  cylinder, 


Fig. 


-FLAN,    FOUR-STAGE    HIGH-I'RESSURE     AIR     COM- 
PRESSOR. 


308  COMPRESSED   AIR    AND    ITS    APPLICATIONS. 

upper  end  of  the  second  intermediate  cylinder,  and  lower  end 
of  the  high-pressure  cylinder,  and  in  its  passage  between  each 
travels  through  one  or  the  other  of  the  coolers. 

The  intercoolers  employed  are  of  two  different  designs.  The 
two  coolers  for  the  lower  pressures  consist  of  a  shell  enclosing 
a  nest  of  vertically  arranged  cooling  pipes  through  which  the 
air  passes  going  from  one  cylinder  to  the  other;  the  coolers  for 
the  higher  pressures  consist  of  a  shell  enclosing  a  pipe  coil,  the 
air  passing  through  the  coil  from  one  cylinder  to  the  other. 
In  providing  a  cooler  for  the  lower  pressures,  where  great  cool- 
ing surface  is  required  on  account  of  the  large  volume  of  air  to 
be  cooled,  it  was  considered  proper  to  provide  tubes,  but  in 
dealing  with  the  cooler  for  the  higher  pressures,  coils  were 
substituted  so  as  to  dispense  with  as  many  joints  as  possible. 
The  coolers  are  arranged  so  that  in  case  of  a  leakage  of  air 
from  the  cooling  pipes  into  the  shell  or  casing,  this  air  rises  with 
the  circulating  water  up  to  the  operating  floor  of  the  engine 
room  and  is  discharged  through  a  sight  discharge  pipe  under 
the  immediate  care  of  the  engineer.  All  the  piping  from  the 
first  air  cylinder  and  through  the  entire  compressing  plant  is 
made  of  copper. 

What  may  be  called  an  auxiliary  governor  controlled  by  air 
pressure  is  provided  to  act  upon  the  governor  of  the  steam 
engine.  This  consists  of  a  weighted  lever  which  is  operated 
upon  by  a  small  piston,  which  in  turn  is  actuated  by  the  air 
pressure.  If  for  any  reason  the  pressure  should  become  exces- 
sive the  lever  is  lifted,  when  it  opens  a  valve  admitting  air  to  a 
device  on  the  governor  so  designed  as  to  reduce  the  steam  sup- 
ply, and  to  all  practical  purposes  throttles  the  engine. 

Compressed  air  for  the  purpose  of  storage  and  traction  by 
the  high-pressure  system  consists  in  reservoir  capacity  due  to  a 
collection  of  steel  bottles,  connected  together  in  series  or  by 
manifolds,  whereby  the  different  sections  of  storage  can  be  cut 
out  from  one  another. 

In  the  storage  system  erected  at  the  Twenty-fourth  Street, 


COMPRESSED-AIR   STORAGE.  3O9 

New  York  City,  compressor  station  there  are  about  600  bottles. 
These  bottles  are  all  tested  to  a  pressure  of  4,500  pounds  per 
square  inch,  and  are  used  to  store  air  at  a  pressure  of  2,500 
pounds  per  square  inch.  There  is  no  wear  and  tear  on  these 
storage  bottles  other  than  can  be  made  good  by  painting  from 
time  to  time.  The  storage  bottles  are  connected  together  with 
proper  pipes  and  valves,  and  communicate  with  several  charg- 
ing stands  in  the  car  house.  The  cars  can  be  charged  with 
compressed  air  at  2,500  pounds  pressure  in  about  two  or  three 
minutes'  time. 

The  Mannesmann  bottles  are  all  tested  to  a  pressure  of 
4,500  pounds  per  square  inch,  and  as  they  are  filled  with  air  at 
a  pressure  of  2,500  pounds  per  square  inch,  there  is  a  factor  of 
safet}'  of  about  2.  The  question  is  frequently  put  as  to  the 
liability  for  these  tubes  to  explode.  When  the  tubes  are  filled 
with  the  air  at  2,500  pounds  per  square  inch  there  is  no  practi- 
cable way  whereby  the  pressure  can  be  increased ;  in  fact,  the 
only  thing  that  can  happen  is  for  the  pressure  to  decrease. 

The  recent  advance  made  in  steel  structural  material  and 
weldless  tubes  has  enabled  the  handling  of  pressures  with  abso- 
lute safety  that  Avere  not  heretofore  thought  possible. 

These  high  air  pressures  mean  greater  mileage  of  cars  and 
vehicles,  so  that  compressed-air  power  has  taken  a  decidedly 
forward  movement  for  railway  and  vehicle  traction. 

THE    COMPRESSED-AIR    BOTTLE    OR    RESERVOIR. 

As  there  has  been  some  misapprehension  in  regard  to  the 
strength  of  the  Mannesmann  air  bottles  or  reservoirs  for  high- 
air  pressures  as  used  on  street  cars  and  vehicles,  we  submit 
some  details  of  tests  made  on  these  tubes  by  the  Watson-Still- 
man  Company  in  presence  of  many  witnesses.  A  Mannesmann 
steel  tube  5  feet  long,  8  inches  diameter,  and  \  inch  thick, 
which  had  been  in  use  on  a  Hardie  motor  for  about  two  years, 
carrying  air  pressure  at  2,000  pounds  per  square  inch,  was  used 
for  the  experiments. 


3IO 


COMl'RESSED    AIR    AND    ITS   APPLICATIONS. 


The  tube  was  first  submitted  to  a  hydraulic  pressure  of 
2,150  pounds,  when  it  was  struck  several  blows  with  a  14-pound 
sledge  having  a  3-foot  handle,  the  sledge  being  swung  from 
the  end  of  the  handle,  and  weighing,  with  the  handle,  16 
pounds.  These  blows  made  no  impression 
whatever.  At  4,000  pounds  the  expansion  was 
found  to  be  three-thirty-seconds  of  an  inch. 
When  the  pressure  was  removed,  the  bottle  re- 
turned to  its  original  measurement,  this  press- 
ure being  near  its  limit  of  elasticity. 

A  second  application  of  pressure  was  then 
made  up  to  5,000  pounds  per  square  inch,  at 
which  point  the  tube  began  to  stretch,  and 
between  5,000  and  6,000  pounds  the  tube  in- 
creased one-eighth  of  an  inch  circumferen- 
tially. 

At  6, 100  pounds  the  bottle  began  to  stretch 
over  a  small  area  at  a  point  near  its  centre, 
and  continued  to  do  so  until  it  was  ruptured, 
at  about  6, 150  pounds  pressure. 

The  character  of  the  rupture  was  a  mere 
split  in  the  steel,  18  inches  long.  No  pieces 
were  detached  and  the  fracture  was  quite 
regular  in  its  form,  showing  high  ductility  in 
the  material  and  freedom  from  any  liability 
to  project  detached  pieces  in  case  of  a  rupture. 
As  the  tube  tested  had  been  in  use  in  one  of 
the  Hardie  air  motors  for  a  period  of  two  years 
under  a  pressure  of  2,000  pounds,  this  indi- 
cated that  there  had  been  no  perceptible  deterioration  in  use,  and 
supported  the  assertion  that  the  duration  of  the  reservoirs  may 
be  considered  as  indefinite,  and  that  no  allowance  in  estimates 
of  cost  of  operation  need  be  made  for  their  renewals  or  repairs. 
Other  tests  have  been  made  of  the  rupture  of  these  tubes, 
one  of  which,  9  inches  in  diameter,  expanded  fifteen-sixteenths 


Fig.    120 —.^ir     bot- 
tle. 


AIR    COMPRESSORS    OF   THE    L.-D.-G.    TYPE.  3II 

of  an  inch  before  fracture,  showing  extraordinary  ductility,  and 
in  all  the  tests  made  in  Germany  and  elsewhere  upon  these 
tubes  no  fragments  were  ever  detached  and  the  fracture  was 
always  of  the  same  character,  a  simple  longitudinal  rent  usually 
near  the  middle  of  the  tube. 

It  appears  that  the  tubes  did  not  begin  to  stretch  until  a 
pressure  of  5,000  pounds  had  been  reached.  Consequently. 
4,000  pounds,  at  which  all  the  tubes  are  tested,  is  below  the 
limit  of  elasticity,  and  2,000  pounds,  which  is  the  maximum 
pressure  under  which  the  reservoirs  are  used  in  the  Hardie 
motors,  must  be  considered  to  be  absolutely  safe  beyond  the 
possibility  of  rupture,  and  even  if  a  rupture  should  occur,  there 
would  be  no  danger  of  flying  pieces  or  of  any  serious  accident. 


COMPRESSORS    OF    THE    LAIDLAW-DUNN-GORDON    CO.AH'AXY, 
CIX'CINXATI.     OHIO, 

Fig.  12  1  illustrates  an  outline  plan  and  elevation  of  the 
duplex  slide-valve  compressor  of  this  company,  of  the  forked - 
frame  type,  and  a  process  print  of  the  same  is  illustrated  in 
Fig.  122.  Large  advantages  in  operation  are  claimed  for  these 
compressors  from  their  straight-line  action  and  the  stability  of 
the  fork  frame,  which  gives  four  bearings  for  a  duplex  com- 
pressor; the  Meyer  adjustable  valve  gear  being  also  a  leading 
feature  in  their  steam  economy.  It  is  adjustable  by  hand,  and 
has  a  range  from  one-fifth  to  four-fifths  cut-oft".  A  separate 
speed  governor  controls  the  general  motion  of  the  engine,  and 
an  unloading  device  unloads  the  work  of  the  engine  when  ex- 
cessive pressure  is  reached,  and  provides  for  its  continuous  mo- 
tion until  a  fixed  minimum  pressure  is  reached  in  the  air  pipes, 
w^hen  the  unloading  device  re.stores  the  compressor  to  its  full 
work.  The  load  relief  prevents  the  compressor  from  stopping 
on  the  centre. 

The  cross-compound,  two-stage  air  compressor  of  this  com- 
pany is  detailed  in   outline  in  Fig.  123,  showing  the  steam  re- 


312 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


ceiver  and  the  intercooler.  The  Meyer  adjustable  cut-off  is 
provided  both  on  the  high-pressure  and  the  low-pressure  cylin- 
ders.    This  compressor  also  has  the  straight-line  action  and  the 


forked  frame  with  centre  crank  for  each  engine.  In  Fig.  124 
is  a  view  of  this  compressor  in  perspective.  The  intercooler  is 
directly  connected  to  the  air  cylinders,  and  the  aftercooler  is 
placed   on    the    air   cylinders  at   the   left.     This   arrangement 


AIR    COxMl'RESSORS    OF   THE    L.-D.-G.    TYl'E. 


3^5 


^ 


314 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


gives  dry,  cool  air  directly  to  the  pipe-distributing  system  and 
avoids  all  possibility  of  oil-vapor  explosions.  The  company 
build   about  twenty  sizes  of  single  and  duplex  compressors  for 


Fig.  123.— cross-compound,  two-stage  compressor. 

pressures  from  35   to    3,000   pounds,  and  of  volumes  from    120 
to  3,000  cubic  feet  per  minute. 


COMPRESSORS    OF   THE    CLAYTON    AIR    COMPRESSOR    WORKS, 
HAVEMEYER    BUILDING,    NEW    YORK    CITY. 

In  Fig.  126  is  illustrated  a  small  post  or  wall  compres.sor 
suitable  for  low  pressures,  up  to  25  pounds,  for  operating  pneu- 
matic appliances  or  oil  burners,  or  for  testing  and  inflating 
pneumatic  tires,  operating  small  sand-blasts,  and  spraying. 
They  are  also  furnished  with  a  crank  handle  for  experimental 
use. 

In   Fig  127  is  illustrated  a  water- jacketed  compressor  of  the 


AIR    COMPRESSORS    OF    THE    L.-D.-G.    TYPE. 


315 


q    ^ 


3i6 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


AIR    COMPRESSORS    OF    THE    CLAYTON   TYPE.  317 


Fig.  126.— post  belt  compressor. 


Fig.  127.— water-jacketed  compressor. 


3i8 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


same  type  as  above;  designed  for  air  pressures  from  lOo  to  250 
pounds  per  square  inch. 

Both  patterns  of  this  compressor  are  made  of  2^,  3,  4,  5,  6, 
and  7  inches  diameter,  by  6  inches  stroke,  and  will  compress 


from  2  to  17  cubic  feet  of  free  air  per  minute  up  to  250  pounds 
per  square  inch  according  to  their  size  and  equipment. 

Fig.  128  shows  a  steam-actuated  air  compressor  for  press- 
ures up  to  25  pounds  with  non- water-jacketed  cylinder.  They 
are  made  in  sizes  from  4  to  12  inches  diameter  of  air  cylinders, 
and  with  steam  cylinders  of  suitable  size  for  the  required  steam 


AIR    COMPRESSORS    OF   THE    CLAYTON   TYPE.  319 

and  air  pressure.  At  their  rating  they  will  compress  25  to  349 
cubic  feet  of  free  air  per  minute. 

In  Fig.  129  is  illustrated  an  electrically  driven  air  compres- 
sor of  the  Clayton  type,  a  most  convenient  method  of  compress- 
ing air  when  an  electric  current  is  available.  It  is  made  in  sizes 
for  small  service. 

In  Fig.  130  is  illustrated  a  duplex  steam-actuated  compres- 
sor of  the  Clayton  type,  which  is  built  in  sizes  of  equal  steam 
and  air  cylinders  from  4  to  10  inches  in  diameter  and  from  5- 
to  9-inch  stroke,  and  at  rated  speed  will  furnish  from  18  to  212 


Fig.  129.— electric-driven  air  compressor. 

cubic  feet  of  free  air  per  minute ;  they  are  water-jacketed  and 
supplied  with  an  automatic  steam  regulator  operated  by  the  air 
pressure. 

The  air  governor  (Fig.  131)  is  located  directly  upon  the 
main  discharge  pipe  of  the  compressor,  with  a  check  valve  in 
the  main  line  at  the  flanges  next  to  the  pressure  gauge  in  the 
figure,  to  prevent  loss  of  air  when  the  compressor  is  unloaded  ;  a 
throttle  valve,  operated  by  a  weighted  lever,  is  operated  at  over 
pressure  by  a  spring-adjusted  piston.  The  small  pipe  at  the 
left-hand  side  of  the  figure  is  screwed  through  the  air  waste  pipe 
and  opens  beneath  the  governor  piston.     Adjustment  is  made 


320 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


AIR    COMPRESSORS    OF    THE    CLAYTON    TYPE. 


321 


by  the  ball  and  a  screw  at  the  top  of  the  piston  cylinder  which 
regulates  the  tension  of  the  piston  spring.  It  is  shown  in  posi- 
tion in  Fig.   132. 

The    three-stage    compressor  (Fig.  133)    is    of    the  Clayton 
model,  and  is  designed  for  high   pressure,  up  to  2,000  pounds 


Fig.  n 


-THE   AIR   GOVERNOR. 


per    square    inch,   and   is   also   arranged    for    compressing   and 
liquefying  carbonic  acid  gas. 

The  steam  cylinders  are  placed  parallel,  as  in  the  regular 
pattern  of  duplex  compressor,  and  the  compressing  cylinders 
are  arranged  in  the  same  manner  at  the  opposite  end  of  the 
frame,  and  at  the  greatest  distance  from  the  heat  of  the  steam 
cylinders.  The  air  or  gas  enters  the  initial  compressing  cylin- 
der, and,  after  undergoing  the  first  compression,  passes  through 
a  coil  surrounded  by  water,  and  thence  into  the  second  com- 
pressing cylinder,  from  which  it  is  transmitted  through  another 


32: 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


AIR    COMPRESSORS    uF    THE    CLAYTON'    TYPE. 


323 


cooling  coil  to  the  third  cylinder,  where  it  undergoes  the  final 
compression.  The  coils  for  cooling  the  air  or  gas  in  transit  be- 
tween cylinders  are  not  shown  in  illustration.  The  cranks  are 
arranged  and  the  cylinders  proportioned  to  provide  for  an  equal 


division  of  load,  and  the  compressor  with  its  steam  cylinders  is 
entirely  self-contained. 

The  proportions  of  this  compressor  are  so  perfect  that  it 
secures  maximum  strength  with  minimum  weight,  together 
with  a  compactness  and  saving  in  floor  space  rarely  obtained  in 
a  machine  of  its  class.     The  fly-wheel  is  placed  in  the  centre 


324 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


avoiding  all  danger  of  injury  through  contact.  The  compress- 
ing cylinders  are  surrounded  by  water-jackets  for  surface  cool- 
ing, and  the  stuffing-boxes  are  also  cooled  by  a  circulation  of 


Fig.  134.— combined  speed  and  air-pressure  governor. 


water.  The  valves,  both  inlet  and  discharge,  and  the  pistons, 
are  of  new  design  and  render  leakage  impossible.  A  satisfac- 
tory method  of  lubrication  is  provided  without  detracting  from 


AIR    COMPRESSORS    OF   THE    GUILD    &    GARRISON    TYPE.       325 

the  purity  of  the  gas,  and  all  the  working  parts  are  singularly 
easy  of  access.  These  are  two  of  the  most  important  features 
of  the  machine,  since  it  is  essential  that  all  parts  coming  into 
contact  with  the  gas  be  kept  free  from  accumulation  of  impuri- 
ties of  any  description,  and  that  they  be  open  to  prompt  adjust- 
ment or  repair. 

The  Clayton  combined  speed  and  air-pressure  governor 
(Fig.  134)  supplies  a  much-needed  want  where  both  engine 
speed  and  air-pressure  regulation  are  required.  It  is  a  combi- 
nation of  the  air  governor  with  a  speed  governor,  and  not  only 
performs  the  functions  of  the  air  governor  already  described 
by  limiting  the  operation  of  the  compressor  to  the  work  re- 
quired, but  also  prevents  the  compressor  from  operating  at  an 
injurious  speed,  should  a  sudden  drop  in  the  air  pressure  pro- ' 
duce  a  greater  demand  upon  the  compressor  than  its  highest 
reasonable  speed  will  supply.  Thus,  should  the  air  be  used  to 
drive  rock  drills  or  hoists,  and  all  of  them  suddenly  be  started 
simultaneously,  the  compressor,  unless  provided  with  a  speed 
governor,  would  run  at  an  excessively  high  rate  of  speed  in 
order  to  supply  the  unusual  demand.  This  applies  in  all  in- 
stances where  the  demand  for  air  is  intermittent.  This  gover- 
nor is  guaranteed  to  control  both  the  speed  of  the  compressor 
and  the  pressure  of  air  with  absolutely  no  attention  from  the 
engineer. 

AIR     COMPRESSORS     MADE     BY     GUILD     &     GARRISON, 
BROOKLYN,    N.    Y, 

Among  the  large  variety  of  air  compressors,  air  and  vacuum 
pumps  made  by  Guild  &  Garrison,  Brooklyn,  New  York  City, 
we  illustrate  the  double-acting  horizontal  air  compressor  (Fig. 
135),  which  has  found  large  employment  in  sugar  refineries, 
chemical  and  fertilizer  factories,  oil  works,  and  other  industrial 
establishments  for  elevating  acids  and  other  liquids,  blowing 
out  filters  and  filter  presses,  aerating  water,  and  for  all  purposes 


326 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


AIR    COMPRESSORS    OF    THE    GUILD    \    GARRISON    TYPE.       327 

in  which   dry  compressed  air  is  required.      It  is  an  excellent 
compressor  for  supplying  air  for  air  hammers  and  drills. 

In  their  style  of  tandem  duplex  single-acting  air  compressor, 
they  have  designed  a  unique  form  of  air  valve,  a  section  of 
which  is  given  in  Fig.  136.  The  inlet  valve  in  the  piston  has 
a  split  gland  guide,  allowing  of  a  ready  means  of  removing  the 


Fig.    136. — GUILD  &   G.\RRISON   COMPRESSOR   VALVE. 

valve  for  repair.  The  discharge  valve  is  a  radical  departure 
from  the  older  designs  of  compressor  valves,  being  a  flat  disc 
valve  covering  the  entire  area  of  the  cylinder  and  held  to  its 
seat  by  a  guide  and  spring.  Its  face  and  the  face  of  the  piston 
are  perfectly  flat,  so  that  the  pi.ston  may  strike  the  valve  and 
deliver  all  the  air  with  no  clearance  space  to  detract  from  its 
efficiency.  A  large  area  of  discharge  is  obtained  by  a  very 
small  movement  of  the  valve,  and  no  pounding  is  made  by  its 
action. 


328 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


AIR    COMPRESSORS    OF   THE    KNOWLES    STEAM    PUMP    WORKS, 
NEW    YORK    CITY. 

In  the  following  pages  we  illustrate  the  various  styles  of  air 
compressors  made  by  this  company,  with  description  appended 
to  each  illustration. 


Fig.  137.— belt  wall  or  post  compressor. 

Capacity,  from  2  to  17  cubic  feet  free  air  per  minute,  and  to  pressures  of  100  to  150  lbs  per 
square  inch.  Piston  diameters,  from  2}4  to  7  inch.  Stroke  of  all  sizes,  6  inch,  single-act- 
ing, without  water-jackets.  Largely  used  where  a  limited  supp'.y  of  compressed  air  is 
required. 


AIR   COMPRESSORS    OF   THE    KNOWLES   TYPE. 


329 


Fig.  1^8.— vertical  geared  and  belt  air  compressor. 


Triplex  type  with  slide  valves  and  unloading  device  by  which  the  load  is  thrown  off  the 
compressor  when  the  pressure  reaches  its  limit  in  the  receiver,  and  again  put  on  when  the 
pressiire  falls  2  or  3  pounds.  A  most  convenient  form  for  low  pressures  up  to  15  pounds. 
Made  in  sizes  from  480  to  3,000  cubic  feet  of  free  air  per  minute. 


330 


CO.Ml'RESSED    AIR    AND    ITS    APl'LICATIONS. 


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AIR    COMPRESSORS    OF   THE    KXOWLES    TYPE. 


331 


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COMPRESSED    AIR   AND    ITS   AITLICATIONS. 


=    £       I 


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AIR    COMPRESSORS    OF   THE    KNOWLES   TYPE. 


333 


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334 


COMrkESSED    AIR    AND    ITS   AlPilCATIONS. 


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AIR   COMPRESSORS    OF    THE    KNOWLES   TYPE. 


335 


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Chapter  XX. 


AIR   COMPRESSORS— Continued 


AIR    COMPRESSORS. 

{CoutiniieiL) 

AIR    COMPRESSORS    OF   THE    NORWALK    IRON    WORKS, 
SOUTH    NORWALK,    CONN. 

The  entire  line  of  compressors  built  b}-  this  company  are  of 
the  compound  type,  in  which  the  heat  of  compression  is  elimi- 
nated as  far  as  possible  between  the  two  stages  of  compression 
by  the  use  of  intercoolers  in  addition  to  the  effect  produced  by 
water-jacketing-  the  cylinders.  The  adoption  of  the  Corliss 
type  of  air  valves  for  both  inlet  and  exit  passages  of  the  low- 
pressure  cylinders  gives  a  full  value  to  the  capacity  of  this  cyl- 
inder to  supply  the  high-pressure  cylinder  to  its  full  capacity  at 
the  discharge  pressure  of  the  low-pressure  cylinder. 

By  this  system  of  compounding  for  the  ordinary  pressure 
used  in  rock-drilling,  pneumatic  tools,  and  the  various  oper- 
ations in  which  the  required  air  pressure  maybe  from  50 to  100 
pounds,  the  economy  in  power  for  operating  the  compressor  is 
very  apparent,  and  is  derived  not  only  from  the  heat  work 
saved  by  intercooling,  but  also  from  the  equalizing  of  the  cylin- 
der pressures  throughout  the  stroke.  This  will  be  readily  rec- 
ognized from  the  fact  that  the  resistance  to  compression  in  the 
low-pressure  cylinder  is  derived  from  a  longer  deliver)'  at  low 
pressure  in  comparison  with  the  action  of  a  single  compression 
to  the  full  pressure. 

x\gain,  in  the  high-pressure  cylinder  the  initial  pressure 
commences  with  the  terminal  pressure  of  the  low-pressure  cyl- 
inder, and  its  delivery  pressure  is  also  extended  over  a  greater 
part  of  the  stroke,  thus  in  a  large  measure  eliminating  the 
otherwise  jerky  action  observed  in  single-cylinder  air  com- 
pression, and  thereby  lessening  the  momentum  work  of  the  fly- 
wheel (see  Table  XIX.  for  the  lost  work  in  single-  and  two- 
stage  air  compression). 
24 


340 


COMPRESSED   AIR   AND    ITS    AI'I'LICATIONS. 


AIR   COMPRESSORS    OF   THE    NORWALK    IRON   WORKS.         34 1 

Under  all  conditions  of  operation  of  a  compound  compressor 
the  risk  of  cylinder  and  receiver  explosions,  from  the  generation 
of  oil  vapor  from  lubricants  by  the  heat  of  compression,  is  en- 
tirely eliminated. 

One  of  the  great  advantages  derived  from  compound  air 
compression  and  intercooling  is  found  in  the  production  of  dry 
compressed  air,  a  valuable  desideratum  when  the  compressed 
air  is  to  be  transmitted  to  a  distance.  Dry  air  prevents  frost- 
ing in  the  transmission  pipe  in  very  cold  weather,  and  the  elim- 
ination of  frost  in  the  exhaust  passages  of  drills  and  pumps  is 
worthy  of  serious  consideration  in  the  choice  of  a  compressor. 

The  double  compound  air  compressor  (Fig.  145)  represents 
in  a  sectional  elevation  the  leading  features  of  construction  in 
the  designs  of  this  company,  in  which  are  shown :  the  Meyer 
adjustable  cut-off  on  the  high-pressure  cylinder;  the  balanced 
slide-valve  on  the  low-pressure  steam  cylinder  with  rock-lever 
connections  with  the  cams  on  the  main  shaft;  a  section  of 
the  Corliss  valves  on  the  low-pressure  air  cylinder,  the  inter- 
cooler  also  in  section  with  the  subdivisions  in  the  intercooler 
heads;  the  air  surface  cooling  tubes  expanded  in  the  sub- 
heads of  the  intercooler;  the  poppet  valves  in  the  high-press- 
ure cylinder  and  the  swivel  cross-head.  The  outside  connecting 
rods  and  details  are  shown  in  the  other  illustrations. 

The  use  of  water  power  is  also  made  available  through  the 
operation  of  a  turbine  or  Pelton  wheel  according  to  the  volume 
or  head  of  the  water  power.  Fig.  146  represents  a  direct-con- 
nected Pelton- wheel  compound  air  compressor,  and  Fig.  148 
represents  a  geared  compound  air  compressor  to  be  operated  by 
a  turbine  or  other  water-power  wheel,  to  which  a  steam  cylin- 
der is  attached  ready  for  connection  when  water  power  fails. 

A  three-stage  air  compressor,  with  two  intercoolers,  is  illus- 
trated in  Fig.  149.  This  is  the  standard  type  for  charging  the 
air  receivers  of  mine  locomotives.  The  steam  end  is  fitted  with 
adjustable  steam  expansion  valves  and  speed  governor. 

In  operation,  the  air  is  brought  from  some  place  cool  and 


)42 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


a     4) 


2    a 


AIR    COMPRESSORS    OF    THE    NORWALK    IRON    WORKS. 


343 


free  from  dust,  and  is  admitted  to  the  large  double-acting  cyl- 
inder in  the  centre  of  the  machine.  Here  the  first  stage  of 
compression  is  performed.  The  water-jacket  by  which  this 
cylinder  is  surrounded  takes  away  a  share  of  the  heat  of  com- 


M  '-• 


pression,  after  which  the  first  intercooler  extracts  the  remain- 
der, bringing  the  air  to  the  second  cylinder  at  or  near  the  tem- 
perature of  the  cooling  water. 

The  second  cylinder  is  also  water-jacketed    and    performs 
another  stage  of  the  compression.     From  this  cylinder  the  air 


344 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


O     0) 

5  ^ 


be  S 


£        5= 


=«  s 

^  ^ 


AIR    COMPRESSORS    OF   THE    NORWALK    IRON    WORKS. 


345 


is  led  through  the  vertical  pipe  shown  in  front  of  the  machine 
to  the  second  intercooler,  and  thence  into  the  third  cylinder 
through  the  inclined  pipe  shown  at  the  back.  In  this  third 
cylinder,  which  is  also  jacketed,  the  compression  is  completed, 
and  the  air  discharged  at  the  connection  shown  at  the  bottom. 


S      13    bfl 


The  pistons  of  the  second  and  third  cylinders  are  in  direct 
line  with  the  piston  of  the  first  cylinder  and  the  steam  piston. 
All  the  strain  of  compression  is  therefore  direct  push  and  pull 
on  a  straight  steel  rod. 

This  compressor  has  a  pressure  capacity  of  about  i,ooo 
pounds  per  square  inch. 


346 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


A  three-stage  air  compressor  suitable  for  a  still  higher  press- 
ure is  illustrated  in  Fig.  150.  Other  air  compressors  of  this 
company  are  illustrated  in  Figs.  147,  151,  152,  and  153,  with 
the  foregoing  general  features,  with  free-air  capacities  of  from 


a;     o 

I       £ 
10       w 


170  to  2,350  cubic  feet  per  minute.  The  sizes  of  the  free-air 
cylinders  vary  from  10  to  32  inches  in  diameter  and  from  12  to 
36-inches  stroke.  Diameters  of  high -pressure  cylinders  about 
two-thirds  the  diameter  of  the  low-pressure  cylinders. 


AIR    COMPRESSORS    OF    THE    XORWALK    IRON    WORKS.        347 


348 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


Fig.    152.  -SMALL-SIZED   CUMI'uL'NLi  AIK   OR   GAS 


;iMPRESSOR. 


Steam  cylinder,  6x8  inch,  with  compound  water-jacketed  cylinders,  for  pressures  from  150 

to  500  pounds. 


Fig.  153.— double  compound  air  compressor. 

Jacketed  air  cylinders  and  intercooler,  with  Corliss  valves  on  low-pressure  air  cylinder. 
Meyer  cut-off  on  high-pressure  steam  cylinder.  Balanced  slide  valve  on  low-pressure  steam 
cylinder. 


AIR    COxMPRESSORS    OF    THE    NOKWALK    IRON    WORKS.        349 


AIR    PRESSURE    REGULATOR. 

The  regulator  of  the  Norwalk  Iron  Works  is  illustrated  in 
Fig.  154.  It  is  placed  in  the  line  of  the  steam  pipe  near  to  the 
steam  cylinder,  the  body  being  a  perfectly  balanced  double- 
seated  valve,  controlled  by  the  air  pressure  in  the  receiver. 
Above  the  regulating  valve  body  is  a  small  cylinder,  having  a 
piston  connected  with  the  bal- 
anced steam  valve  below  by  a 
stem  as  shown  in  the  illustra- 
tion. Above  the  small  piston  is 
a  stop  screw  projecting  above  the 
cylinder  head  for  regulating  the 
lift  of  the  piston  by  the  com- 
pressed air  pressure  beneath  it. 
The  air  from  the  receiver  is  led 
through  a  small  safety-valve 
shown  on  the  left  side  of  the  cyl- 
inder in  the  illustration,  which 
regulates  the  pressure  at  which 
the  air  can  enter  the  cylinder  and 

close  the  balanced  valve.  Above  the  disc  of  the  small  safety- 
valve  is  a  spring  whose  tension  to  close  the  valve  is  regulated 
by  a  screw  with  a  milled  head,  allowing  the  spring  tension  on 
the  valve  to  be  so  adjusted  that  the  valve  will  lift  and  permit 
the  air  from  the  receiver  to  flow  under  the  piston,  and  by  its  lift 
close  the  balanced  valve.  The  air  passes  into  the  small  cylin- 
der beneath  the  piston,  and  if  no  escape  w^ere  provided  would 
drive  the  piston  to  the  top  of  the  cylinder.  To  regulate  this 
action  a  very  fine  slot  is  cut  in  the  side  of  the  small  cylinder. 
When  the  piston  rises  it  uncovers  this  slot  and  thus  furnishes 
an  escape  for  the  air  which  is  passing  the  safety-valve.  If  only 
a  little  air  passes  the  valve,  then  a  small  part  of  the  slot  will  ac- 
commodate it  and  the  piston  will  take  a  low  position.  With 
more  air  escaping,  the  piston  will  rise  higher  and  uncover  more 


Fig.  154.— regulator. 


JD^ 


comfkessp:d  air  and  its  applications. 


of  the  slot,  thus  providing  a  larger  opening  for  its  exit.  As  the 
slot  is  very  fine,  a  very  little  difference  in  the  quantity  of  air  will 
cause  the  piston  to  assume  a  high  or  low  position.  After  the 
small  safety-valve  begins  to  blow,  an  almost  insensible  increase 
of  pressure  in  the  reservoir  will  furnish  enough  more  air  to 


IIIIIIIIINIIIIII IIIIIIIIIIIIIUIIIIII.S 


Fli;      1        — \  I  i<     1     W     I  I  I   1  1  I)   DUPI  r  X    AIK   (  OMPKFbbOR 
Type  of  the  Edward  P.  AUis  Company,  Milwaukee.  Wis.     With  Corliss  air  valves. 


carry  the  piston  to  the  top  of  the  small  cylinder.  Thus  any 
degree  of  regulation  is  obtained  by  a  very  little  difference  of 
pressure.  As  the  air  which  works  on  the  piston  in  the  small 
cylinder  has  only  to  perform  the  work  of  lifting  the  piston  and 
valve  sufficiently  to  uncover  enough  of  the  slot  so  that  it  can 
escape,  its  pressure  is  very  slight.     The  piston  is  fitted  loosely, 


AIR   COMPRESSORS    OF    THE    E.    P.    ALLIS   CO. 


351 


Fig.  136— compound  corlihs  engine-driven  hlowing  engine. 

Vertical  type  for  blast  furnace  and  bessemer  work.     Built  by  the  Kdward  P.  Allis  Company, 

JMilwaukee,  Wis. 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


2     M 


a    * 


5    ^ 


AIR   COMPRESSOR   OF   THE    MERRILL   TYPE. 


353 


and  the  whole  apparatus  moves  as  nearly  without  friction  as 
can  be  imagined. 

When  this  regulator  is  applied  to  compressors  having  a  sin- 
gle steam  cylinder  it  is  possible  for  the  valve  to  be  carried  so 
high  as  to  shut  off  all  steam  and  stop  the  engine  on  the  centre. 
This  would  be  objectionable.  To  obviate  this  there  is  placed 
on  the  top  of  the  small  cylinder 
a  screw  stop  which  can  be  set  to 
prevent  the  closing  of  the  steain 
valve  more  than  is  sufficient  to 
run  the  engine  at  the  slowest 
speed  at  which  it  will  pass  the 
centre. 

The  Corliss  air-valve  gear  of 
this  company  is  somewhat  pe- 
culiar; the  valves  are  moved  b}' 
cams.  The  shape  of  these  cams 
is  such  that  the  valve  remains 
at  rest  until  the  pressure  below 
it  is  nearly  equal  to  that  above. 
Then  the  movement  begins,  and 
when  the  pressures  are  equal 
the  valve  is  quickly  thrown  full 
open.  In  closing,  the  cam  allows 
a  rapid  movement,  so  that  the 
valve  is  seated  before  any  con- 
siderable pressure  comes  upon 
it.      The  connection  which  draws 

it  shut  is  elastic,  so  that  if  the  valve  seat  is  dry  no  cutting  can 
occur.  This  form  of  movement  having  such  desirable  features 
for  heavy  pressure  is  in  a  degree  useful  at  any  pressure,  and  has 
been  therefore  adopted  for  this  company's  standard  compressors. 

The   Merrill   compound   direct-acting  air  compressor  (Fig. 
158)  is  one  of  the  latest  productions  for  the  economical  com- 
pression of  air  for  pumping  water  by  the  direct  displacement 
22, 


Fig.  158.— compound  direct-acting  air 
compressor. 


354  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

and  inductor  system,  and  for  the  lesser  requirement  for  pneu- 
matic tools.  It  is  an  improvement  upon  the  wasteful  method 
of  the  direct-acting  air-brake  pump,  and  claims  a  high  efficiency 
for  a  vertical  direct-acting  type.  Its  action  is  derived  from 
three  steam  pistons  and  three  air  pistons,  each  pair  of  steam 
and  air  pistons  on  a  piston  rod,  and  all  three  pairs  being  con- 
nected together  by  a  cross-head,  which  carries  a  diagonal  valve 
gear  that  shifts  the  ports  of  the  steam  valve  by  rotating  a 
ported  piston,  which  in  turn  throws  a  spool-valve  linked  to  a 
slide-valve.  There  are  one  high-pressure  and  two  low-pressure 
cylinders  for  both  steam  and  air.  Air  cylinders  are  water- 
jacketed.  The  central  cylinders  for  both  steam  and  air  are 
high  pressure;  the  outside  are  low  pressure,  so  that  each  pair 
of  steam  and  air  cylinders  is  equalized  as  to  strains.  The 
low-pressure  steam  cylinders  are  cushioned  sufficiently  to  pre- 
vent their  pistons  from  striking  the  heads  imder  any  condi- 
tions of  air  compression.  An  intercooler  is  provided  in  the 
base  of  the  compressor, 

AIR     COMPRESSORS      OF     THE      CURTIS    &    CO.    MANUFACTURING 
COMPANV,    ST.    LOUIS,    MO. 

In  the  following  figures  are  illustrated  the  various  styles  of 
air  compressors  made  by  this  company.  They  are  principally 
designed  for  use  in  shops  and  foundries,  and  for  the  requirements 
of  small  operators  with  compressed  air.  In  Fig.  159  is  repre- 
sented the  duplex  single-acting  belt-driven  compressor,  which 
is  built  in  two  sizes,  6x6  and  8X8  inches,  piston  and  stroke. 

A  section  of  the  working  parts  is  shown  in  Fig.  160,  and  the 
valve  seat  and  valve  cap  in  Figs.  161  to  164.  The  working 
parts  are  entirely  enclosed  in  order  to  exclude  the  dust  of  a 
shop  from  the  valves  and  cylinders.  The  trunk  pistons  are 
packed  with  metallic  rings,  and  the  cylinders  and  heads  water- 
jacketed. 

In  Fig,  165  is  represented  the  duplex  single-acting  com- 
pressor with  a  vertical  steam  engine  all  mounted  on  a  single 


AIR    COMPRESSORS    OF   THE    CURTIS   &    CO.    TYPE. 


355 


base.  In  this  arrangement  the  engine  crank  is  set  at  right 
angles  with  the  compressor  cranks,  so  that  the  greatest  resist- 
ance during  compression  receives  the  highest  pressure  in  the 
steam  cylinder. 

The  working  parts  of  this  compressor  are  shown  in  section 
on  preceding  page. 

In  Fig.  1 66  is  shown  a  sectional  elevation  from  the  drawing 


Fig.  159.— duplex  vertical  air  compressor. 
Belt  di-iven. 


of  the  belt-driven  compound  or  two-stage  compressor  of  the 
Curtis  Company,  the  cylinders  of  which  are  13  and  8  inches 
diameter  by  12 -inch  stroke,  with  an  intercooler  shown  in  the 
vertical  section  on  the  next  page. 

The  general  construction  and  valves  are  the  same  as  in 
other  compressors  of  this  company.  Capacity  at  120  revolutions 
is  100  cubic  feet  of  free  air  per  minute  at  100  pounds  pressure. 


356 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  ifio.-  section. 


AIR    COMPRESSORS    OF   THE    CURTIS   &    CO.  TYPE. 


357 


A  larger  size  on  the  same  plan  has  a  capacity  of  200  cubic  feet 
per  minute. 

In  Fig.  167  is  a  sectional  end  elevation  of  the  smaller  cylin- 
der showing  the  air  inlet  from  the  intercooler,  valve  location, 


0 


Fig.  161.— valve.  Fig.  162.— valve. 

and  air  discharge,  figured  on  the  same  scale  as  the  front  section 
on  previous  page. 

These  compressors  are  provided  with  both  an  air-pressure 
and  speed  governor.  The  air-pressure  governor  automatically 
stops  the  compression  of  air  without  stopping  the  machine. 

The  gas  and  gasoline  engine  compressor  of  this  company 
(Fig.  168)  is  a  most  compact  arrangement  suited  for  supplying 
compressed  air  for  hammers  and  riveters  in  construction  work. 


Fig.  163.— seat. 


Fig.  164.— cap. 


The  air  cylinders  are  single-acting  and  connected  by  gearing  to 
the  gas  or  gasoline  engine  so  that  the  engine  makes  two  revo- 
lutions to  one  of  the  compressor.  The  cranks  are  so  arranged 
that  the  motor  stroke  of  the  engine  corresponds  with  the  com- 
pressing stroke  of  the  compressor.  Cylinders  of  engine  and 
compressor  are  water-jacketed.  They  are  built  for  free-air 
capacity  from  25  to  200  cubic  feet  per  minute. 


358 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Fig.  165.— steam  driven  duplex  compressor. 
Mounted  on  common  base. 


AIR    COMPRESSORS   OF   THE   CURTIS   &    CO.    TYPE. 


359 


No.  2  Lunken 


HVipe 


%  Drain. 


Fig.  i66.— section  of  belt-driV'EN  compound  aik  compressor. 


36o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


— 2  11%- 


FlG.    167.— END  SECTIONAL  ELEVATION    OF  COMPOUND  AIR   COMPRESSOR. 

Showing  location  of  intercooler. 


AIR   COMPRESSORS    OF   THE    N,   Y.  AIR   COMPRESSOR    CO.       36 1 


Fig.    168. -the   GAS-ENGINK   AIK   CDMfKESSUK. 


AIR     COMPRESSORS     OF    THE     NEW     YORK    AIR    COMPRESSOR 

COMPANY. 

The  compressors  of  this  company  have  been  designed  espe- 
cially for  supplying  compressed  air  for  the  operation  of  pneu- 
matic hammers,  drills,  riveters,  hoists,  and  other  tools  used  in 
shop  and  construction  work,  although  equally  applicable  to 
driving  rock  drills,  coal-cutters,  and  other  mining  machinery, 
pumping  water  by  the  air-lift  system,  operating  signals,  clean- 
ing cars  and  cushions,  elevating  acids,  and  other  uses  of  com- 
pressed air. 

The  Corliss  type  of  compressor  shown  in  Fig.  169  is  em- 
ployed   in    installations    of   large    capacity,   and    is    built  with 


362 


COMPRESSED    AIR    AND    ITS    Ari'LICATIONS. 


duplex  or  compound  steam  or  air  cylinders,  either  condensing 
or  non-condensing. 

The  compressor  shown  in  Fig.  170  has  duplex  steam  cylin- 
ders with  Meyer  adjustable  cut-off,  and  compound  air  cylinders 


Fig.  169.— the  CORLISS  tvpe. 

with  intercooler.  This  compressor  is  built  in  four  sizes,  rang- 
ing in  capacity  from  500  to  2,000  cubic  feet  of  free  air  per  min- 
ute, and  when  the  available  steam  pressure  is  sufficiently  high 
the  steam  cylinders  are  compounded  also.  The  intercooler 
consists  of  a  set  of  composition  metal  tubes  encircled  by  a  steel 


'^nllp      11..^ 

.1     .; 

mm 

Fig.  170.— the  duplex  type. 

shell,  the  cooling  water  passing  through  the  tubes  and  the  air 
circulating  around  them. 

The  duplex  steam-driven  air  compressor  of  this  company  is 
illustrated  in  Fig.  171.  It  has  cylinders  and  heads  water- 
jacketed,  and  is  provided  with  both  speed  and  pressure  control- 


AIR    COMPRESSORS   OF   THE   N.    Y.    AIR    COMPRESSOR    CO. 


O'-'O 


lers.     The  large  sizes  are  built  with  the  Meyer  adjustable  cut- 
off, a  most  substantial  and  efficient  compressor  for  any  work. 


tji      1         1 

:- 

^^9^ 

H*-            9 

■ 

M^^^ 

i^_^ 

ji 

Vi^M*^^g>  ~  %7^V7^^H 

^^S 

— .i — ^n 

Fig.  171.— duplex  type  with  governor. 

They  are  made  in  sizes  of  7  X  /-inch  air  cylinders  with  equal- 
sized  steam  cylinders,  and  in  five  sizes  up  to  16  X  18-inch  air 
cylinders  with  equal-sized  steam  cylinders,  and  of  capacity  from 
80  to  1,000  cubic  feet  of  free  air  per  minute. 

Fig.    172  represents  a  single  straight-line  steam-driven  air 
compressor,  also  built  by  the  same  company.     This  type  is  ad- 


FlG.    172.— STR.\IGHT-LINE   COMPRESSOR. 


vantageous  for  field  work  and  for  other  classes  of  service  pre- 
senting conditions  rendering  the  single  style  of  compressor 
preferable  to  the  duplex. 


3^4 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


Fig.  173  illustrates  a  horizontal,  duplex,  belt-driven  air  com- 
pressor with  air-pressure  controller  that  unloads  the  work  of  the 
compressor   whenever    an    over-pressure    is    attained    by    the 


Fig.  173.— duplex  belt  compressor. 

Stoppage  of  work  on  air  tools.  They  are  made  in  air-cylinder 
sizes  from  7  X  7  to  16  X  18  inches,  and  of  capacity  from  80  to 
1,000  cubic  feet  of  free  air  per  minute. 

The  single  style  of  belt-driven  air  compressor  shown  in  Fig. 
174  is  adapted  to  the  same  service  as  the  duplex  machine  last 


blG.   174.  — SINGLE   BELT   COMPRESSOR. 


described,  and  is  sometimes  preferred  because  of  the  more  lim- 
ited floor  space  occupied  by  it.  This  compressor  is  built  in 
sizes  ranging  from  100  to  500  cubic  feet  of  free  air  per  minute, 


AIR    COMPRESSORS    OF    THE    N.   Y.   AIR    COMPRESSOR    CO. 


565 


and  is  provided  with  automatic  unloading  device  for  controlling 
its  operation  to  suit  the  demand  made  upon  it. 

The  vertical  air  compressor,  belt-driven  (Fig.    175),  is  pro- 


FlG.   175.— THE   VERTICAL  AIR  COMPRESSOR. 


vided  with  water-jacketed  cylinders  and  heads;  a  substantial 
machine,  with  poppet  valves,  and  suitable  for  any  pressure 
used  in  shop  and  constructive  work. 


Chapter  XXI. 


AIR  COMPRESSORS— Continued 


367 


AIR    COMPRESSORS. 

{Contimied.) 

AIR    COMPRESSORS    OF    THE    RAND    DRILL    COMPANY, 
NEW    YORK    CITY. 

Figs.  176  and  177  show  the  standard  forms  of  the  air  cylin- 
ders of  this  company,  which  are  water-jacketed,  and  in  some  of 
the  designs  the  heads  are  also  water- jacketed.  Valves  are  of 
the  poppet  type. 

The  unloading  device  by  the  opening  of  a  valve  from  exces- 
sive pressure  allows  the  air  on  the  compression  side  of  the  pis- 


FIG.   176. -AlK    CYLINDER   WITH    HOODED   HEADS  AND   POPrET    VALVES. 

ton  to  pass  over  to  the  inlet  side  and  thus  relieve  the  piston  of 
its  load  until  the  receiver  pressure  falls  below  the  working 
pressure,  when  the  weight  closes  the  valve  and  the  compressor 
resumes  its  work. 

The  air-valve  gear  of  this  company  is  a  novelty  in  valve  con- 
trol.    Experience  has  shown  that  the  ordinary  poppet  valves 


370  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

as  usually  held  under  a  spring  are  liable  to  chatter  more  or  less, 
and  that  by  making  the  springs  stronger  to  reduce  the  chatter- 
ing the  lift  of  the  valves  is  also  reduced,  which  restricts  admis- 
sion, and  therefore  a  larger  number  of  inlet  valves  are  required 
or  the  efficiency  of  the  compressor  is  lessened. 

The  mechanical  poppet-valve  gear  shown  at  Fig.  179  has  a 
yoke  frame  at  each  end  of  the  cylinder  connected  by  outside 
rods.     To  the  yoke  frames  the  inlet  and  outlet  valves  are  con- 


FlG.   177.— THE  LNLOADING   DEVICE  FOR   A   BELT   COMPKESSOR. 

nected,  not  rigidly,  but  with  spring  tension,  so  that  all  the 
valves  have  a  positive  movement  at  the  proper  moment  to  a 
wide-open  or  closed  position,  the  springs  operating  to  soften 
the  impact  of  the  valves.  The  valve  gear  is  operated  from  an 
eccentric  on  the  main  shaft. 

The  valves  thus  operated  have  their  equivalent  area  largely 
augmented,  and  thus  require  a  less  number  of  valves  to  a  cylin- 
der than  when  fitted  with  the  ordinary  poppet  valve  with 
springs  only. 

In  Fig.  181  is  illustrated  the  complete  cross  compound  Corliss 
air  compres.sor  of  the  Rand  Drill  Company,  in  which  the  low- 
pressure  cylinder  is  provided  with  the  Corliss  inlet  valve,  the 


AIR   COMPRESSORS    OF   THE    RAND    DRILL   COMPANY.  371 


>    E 


o 


S     S 


i/- 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Fig.  179.— the  kand  aik  valve  gear. 


Fig.  180.— the  CORLISS  inlet  valve  ;  poppet  discharge  valves. 


AIR    COMPRESSORS    OF   THE    RAND    DRILL   COMPANY.  373 


374 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


discharge  and  high -pressure  valves  being  of  the  free  poppet 
type.  The  box-like  connection  between  the  cylinders  contains 
the  intercooling  pipe  coil  as  shown  in  the  section  on  intercooling. 
Fig.  183  represents  the  cross  compound  steam  and  air  cylin- 
der type  of  this  company,  with  removable  water  jackets  on  the 
air  cylinders — a  valuable  consideration  for  the  efficiency  of  an 


Fig.   182.  -AIK    CYLIXDEK  ;  CORLISS   INLET   AND   DISCHARGE   VALVES. 


air  compressor  where  limy  or  muddy  water  must  be   used  for 
cooling  cylinders  and  intercooler. 

In  the  various  sizes  and  combinations  of  the  compressors  of 
the  Rand  Drill  Company,  numbering  about  twenty,  the  capaci- 
ties vary  gradually  from  350  to  6,000  cubic  feet  of  free  air  per 
minute.  The  compound  or  two-stage  compressors  are  intended 
for  final  pressures  up  to  100  pounds  pressure  per  square  inch. 
In  the  low-pressure  cylinder,  compression  takes  place  from 
atmospheric    pressure    to  27   pounds,    delivering  to  the    inter- 


AIR    COMPRESSORS    OF   THE    RAND    DRILL    COMPANY. 


375 


Fig.    1S3.  — cross  compound  steam   ANU  air   CYLINDERb. 

With  removable  water  jackets  and  intercooler. 


Fig.  "184.  — THE   IMPERIAL  TYPE   AIR   COMPRESSOR. 


376 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


cooler  at  about  240°  F.  and  to  the  high-pressure  cylinder  at 
normal  temperature.  When  the  full  pressure  of  100  pounds  is 
obtained  the  air  is  delivered  at  a  temperature  of  240°  F.,  or  in 
the  like  proportion  for  other  required  working  pressures,  vary- 
ing from  50  to  1 10  pounds  per  square  inch. 

A  new  design  of  self-contained  duplex  or  compound  air  com- 
pressor has  been  brought  out  by  the  Rand  Drill  Company  (Fig. 
184),  in  which  the  steam  and  air  piston  rods  are  connected 
by   a  yoke   within    which    the    crank    and    connecting-rod    are 

contained.  Cranks  at  right 
angles,  with  heavy  central  fly- 
wheel, and  all  cylinders  over- 
hung. Inlet  valves  of  Corliss 
type  driven  from  eccentrics  on 
shaft  with  poppet  discharge 
valves.  The  bath  system  of 
lubrication  is  provided  for  the 
main  bearings,  crank  pins, 
crosshead  slides,  and  eccentric 
straps,  the  oil  being  distrib- 
uted by  the  dip  of  the  crank 
discs. 

This  type  of  compressor  is 
made  in  six  sizes  with  capaci- 
ties from  140  to  1 ,000  cubic  feet 
of  free  air  per  minute.  The 
fly-wheel  has  a  broad  face,  crowned  to  receive  a  driving  belt,  so 
that  the  compressor  may  be  driven  by  other  machinery,  or  may 
drive  other  machinery  if  required. 

The  Imperial  belt  compressor  of  this  company  (Fig.  185)  is 
of  the  vertical  type  with  single-acting  trunk  pistons  connected 
to  cranks  set  opposite  to  each  other.  The  belt  pulley  is  very 
large  and  heavy  with  broad  face  to  give  ample  power  direct  from 
the  belt.  For  pressures  above  2  5  pounds  the  cylinders  are  water- 
jacketed.     Inlet  and  outlet  valves  are  of  the  poppet  type.     The 


Pig.  185.— imperial  belt  compressor. 


AIR    COMPRESSORS    OF    THE    RAND    DRILL    COMPANY. 


\n 


inlet  valves  of  both  cylinders  have  a  common  passage  which  can 
be  connected  to  an  air  pipe  from  outdoors  for  cool  air  free  from 
dust.  It  is  designed  as  a  special  air  compressor  for  shop  tools, 
hammers,  chisels,  riveters,  etc.,  and  has  an  unloading  device  that 
stops   the   compression   of  air  without  stopping  the  machine. 


Fig.  i86.— high-pressure  compressor. 


when  the  pressure  reaches  its  limit.     It  is  made  in  seven  sizes 
of  capacity,  from  ii  to  275  cubic  feet  of  free  air  per  minute. 

STEAM-ACTUATED    HIGH-PRESSURE    COMPRESSORS. 

In  Fig.  186  is  illustrated  the  small  vertical  two-stage  com- 
pressor with  box  water  jacket  for  high  pressures.  In  these 
compressors  the  entire  air  cylinders  and  connecting-pipes  are 
covered  with  a  large  body  of  water,  which  insures  a  thorough 
cooling  of  the  air  or  gas  throughout  the  operation  of  compres- 
sion. They  are  in  use  for  the  production  of  liquid  carbonic 
acid  gas,  and  work  up  to  a  thousand  or  more  pounds  per  square 
inch. 


378 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


Fig.  187.— high-pressure  compound  compressor. 


Fig.  i88.-three-st.\ge  co.mpkessor. 


AIR   COMPRESSORS    OF   THE    RAND    DRILL   COMPANY. 


379 


Fig.  187  represents  the  same  style  of  compound  compressor 
with  jacketed  cylinders  and  intercooler;  front  and  side  view. 

In  Fig.  188  is  represented  the  three-stage,  high-pressure, 
steam-actuated  compressor  of  the  Rand  Drill  Company  for  com- 
pressing air  to  very  high  pressures,  2 ,  500  pounds  or  more.  This 
type  of  compressor  is  much  used   for  liquefying  carbonic  acid 


-FOUR-STAGE   Alk    A> 


gas  and  for  compressing  oxygen,  hydrogen,  and  other  gases  for 
experimental  work  and  for  transportation  in  steel  bottles. 

Fig.  189  represents  the  four-stage  air  and  gas  compressor. 

In  Figs.  190  and  191  are  illustrated  the  direct-acting  air 
compressors  of  the  Marsh  type,  built  by  the  American  Steam 
Pump  Company.  A  model  type  of  portable  and  light  construc- 
tion, suitable  for  operating  pneumatic  tools. 

Fig.  192  represents  the  duplex  vertical  air  compressor  of 
the  St.  Louis  Steam  Engine  Company. 


38o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  190.— air  compressor,  American  steam  pump  company,  battlk  creek,  mich. 

Direct  acting. 


Fig.  191.— air  compressor,  American  steam  pump  company. 

Direct  actiiv^.     Smallest  size,  1%  >C  z-inch  air  cylinder. 


AIR    COMPRESSORS    OF   THE    ST.   LOUIS    S.   E.   COMPANY.       38 1 


Fig.  192.— vertical  duplex  air  compressor. 

St.  Louis  Steam  Engine  Co.    Three  sizes  built— 6  x  6,  7  x  7,  8  x  8.     Supplying  from  50  to  120 
cubic  feet  of  free  air  per  minute. 


382 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


AIR    COMPRESSORS    AND    BLOWING     ENGINES    OF     THE     PHILADEL- 
PHIA   ENGINEERING    WORKS,    LTD. 

This  company's  air  compressors  and  blowing  engines  for 
blast  furnaces  are  fitted  with  the  Corliss  steam  and  Gordon  air- 
valve  gear.  In  Fig.  193  is  shown  the  operation  of  the  posi- 
tive valve  system  in  these  compressors.  The  inlet  valves  are 
opened  and  closed  by  an   eccentric  operating  directly  through 


Fig.  193.— the  CORLISS  air  compressor  cylinder. 
With  Gordon  valve  movement. 


the  wrist  plate.      The  outlet  valves  are  operated  by  the  same 
wrist. 

The  outlet  valves  are  opened  when  the  pressure  within  the 
cylinder  reaches  that  of  the  discharge,  and  are  closed  from  the 
action  of  the  same  wrist  plate  that  operates  a  spool  piston  in 
an  auxiliary  cylinder  for  each  discharge  valve,  one  end  of  which 
is  larger  than  the  other.  The  larger  end  is  in  constant  con- 
nection with  the  compression  cylinder  and  the  smaller  end  with 


AIR    COMPRESSORS    OF    THE    D'AURIA    TYPE. 


3^3 


the  discharge  chamber,  the  office  of  which  is  to  relieve  the  fric- 
tion on  the  Corliss  valve  and  throw  it  wide  open  at  the  moment 
that  the  pressures  in  the  cylinder  and  discharge  chamber  are 
equal. 


A     HYDRAULIC-CONTROLTED     DIRECT-ACTING     AIR     COMPRESSOR. 

In  Fig.  194  is  represented  a  new  departure  in  the  construc- 
tion of  direct-acting  air  compressors. 

The  D'Auria  air  compressor  is  a  non-rotative  compressor  of 
the  duplex  type.     vSo  far  as  steam  economy  is  concerned,  it  may 


Fig.    194.- D'AURIA    NON-ROTATIVE   AIR   COiMPRKSSOR. 

be  said  to  have  less  limitations  than  even  a  crank  and  fly-wheel 
compressor,  for  the  simple  reason  that,  while  in  the  latter  the 
high  degree  of  steam  expansion  calls  for  heavier  fly-wheels, 
heavier  crank  shafts,  etc.,  the  moving  parts  of  the  D'Auria 
compressor  are  not  in  the  least  affected  by  the  degree  of  steam 
expansion,  and  the  machine  works  equally  well  with  a  high  or 
with  a  low  expansion. 

Since  there  is  no  mechanism  of  fly-wheels,  connecting-rods, 
and  crossheads  employed  to  equalize  the  propelling  force  and 
the  resistance  at  every  point  of  the  stroke,  the  question  arises, 


384 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


How  is  perfectly  smooth  action  attained  in  the  D'Aiiria  com- 
pressor, starting  the  stroke  with  a  high  initial  pressure  of  steam 
against  no  resistance,  and  ending  the  stroke  with  a  propelling 
force  practically  nil  and  with  resistance  at  a  maximum  ? 

This  result  is  accomplished  by  a  "hydraulic  compensator," 
which  is  a  cylinder,  A  A,  Fig.  195,  fitted  with  a  plunger,  B, 
carried  by  the  same  piston  rod  which  connects  the  steam  and 
the  air  piston.  The  ends  of  the  compensator  cylinder  commu- 
nicate with  each  other  by  means  of  a  loop  of  pipe,  C  C  C,  turned 


Check       <^'^''  ''«'"' 
ValveU 


rra 


'\lr.^  -.,-:M 


Fig.  195 —section  d'aukia  air  comhressok. 


into  the  form  of  a  very  rigid  bed-plate,  which  adds  to  the 
strength  of  the  machine  and  preserves,  under  all  conditions, 
the  alignment  of  the  piston  rod.  This  cylinder  and  pipe  are 
filled  with  water  or  any  other  liquid;  and  as  there  is  no  loss 
of  liquid  be5^ond  that  which  may  leak  through  the  stuffing- 
boxes,  they  are  easily  kept  full  from  any  source  of  water 
supply,  through  the  small  pipe  and  two  check  valves,  shown 
in  Fig.  195. 

When  the  compressor  is  in  action,  the  liquid  column  con- 
tained in  the  compensator  pipe  is  affected  reciprocally,  to  and 
fro,  by  the  plunger,  and  acts  in  exactly  the  same  manner  as  a 
balance  wheel  in  a  watch,  taking  up  the  excess  of  energy  in  the 
first  half,  and  giving  it  back  in  the  second  half  of  the  stroke 
with  an  exceedingly  small  loss  due  to  friction. 

These  compressors  have  no  dead  centres.  The  cycle  of  their 
action  being  limited  to  the  period  of  one  stroke,  they  are  able  to 


AIR    COMPRESSORS    OF    THE    ELECTRIC    TYPE. 


385 


start  and  stop  instantly,  and,  if  fitted  with  a  sensitive  pressure 
regulator,  will  stop  completely  on  a  small  variation  of  air  press- 
sure,  and  will  start  promptly  when  that  pressure  falls  slightly 
below  the  normal.  They  are  also  built  with  compound  steam 
and  air  cylinders. 

These  compressors  are  the  invention  of  Mr.  Luigi  d'Auria, 
of  Philadelphia,  and  are  manufactured  by  the  D'Auria  Pumping 
Engine  Company,  Drexel  Building,  Philadelphia,  Pa. 


Fig.  196.— the  electric-driven  air  compressor. 

Vertical  type,  directly  geared  to  an  electric  motor.     Built  in  seven  sizes,  single,  of  free-air 
capacity  from  5  to  170  cubic  feet  per  minute. 


386 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


AIR    COMPRESSORS    OF   THE    STILLWELL-BIERCE   &    SMITH-VAILE 
COMPANY,    DAYTON,    OHIO. 

These  air  compressors  are  built  in  several  combinations  and 
of  a  large  number  of  sizes,  from  20  to  1,400  cubic  feet  of  free 
air  per  minute. 


AIR   COMPRESSORS    OF   THE   S.-B.  &   S.-V.  COMPANY. 


387 


388 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


S    ^ 


AIR    COMPRESSORS    OF    THE    S.-B.  &    S.-V.   COMPANY. 


389 


S    0) 


390 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  20I.— THK  FISHEK   AIK  COMPRESSOR. 


Fig.  202.— lever  air  pump. 


Fig.  203.— post  lever  air  pump. 


AIR    COMPRESSORS    OF    THE    SEDGWICK-FISHER    COMPANY.    39I 

In  Fig.  201  we  illustrate  the  Fisher  air  compressor  made  by 
the  Sedgwick-Fisher  Company,  Chicago,  111.  Its  principal 
novelty  is  the  facility  of  its  attachment  to  any  engine  by  ex- 
tending the  engine  piston  rod  through  the  back  head  and  con- 
necting it  to  the  piston  rod  of  the  compressor,  the  air  cylinder 
being  connected  by  stay  rods  to  the  back  head  of  the  engine. 
This  seems  to  be  a  most  economical  method  of  installing  a  com- 
pressed-air plant  in  shops  and  mills  where  the  engine  is  not 
doing  full  duty.  The  plant  as  illustrated  is  in  operation  in  vS. 
Freeman  &  Sons'  Works  at  Racine,  Wis. 

Apart  from  the  bicycle  air  pump  for  its  special  work,  there 
is  no  small  air  compressor  so  convenient  for  quick  service  as 
the  table  pump  (Fig.  202),  and  the  post  pump  (Fig.  203).  The 
first  can  be  screwed  to  a  table  or  bench,  and  the  second  can  be 
screwed  to  a  post,  for  any  service  under  150  pounds  pressure 
per  square  inch.  They  are  furnished  by  the  Gleason-Peters 
Air  Pump  Company,  New  York  City. 

The  action  of  the  lever  is  such  that  the  leverage  increases 
with  the  increase  of  pressure  by  compression,  a  most  desirable 
requisite  in  a  hand-operated  air  pump.  The  air  capacity  is 
about  36  cubic  inches  of  free  air  per  stroke. 

AIR    COMPRESSORS     OF     THE     NORDBERG     MANUFACTURING 
COMPANY,    MILWAUKEE,    WIS. 

We  illustrate  in  Fig.  204,  and  following,  the  air  compressors 
of  the  above  company  and  the  leading  features  of  their  design. 
The  valve  gear  consists  of  a  triple  wrist  arm  running  on  a 
strong  trunnion  bolted  to  the  cylinder,  an  eccentric  on  crank 
shaft  connected  to  the  wrist  arm  by  an  intermediate  carrier  arm. 
The  connecting  rods  between  the  wrist  arm  and  the  valve  arms 
are  arranged  for  a  quick  and  full  opening  and  closing  of  the 
inlet  valves,  while  the  setting  of  the  valves  is  made  by  adjust- 
ing screws  on  the  hub  of  the  valve  arms. 

In  Fig.  205  is  shown  the  unloading  device,  which  is  a  re- 


392 


COMPRESSED    AIR   AM)    ITS    AI'I'LICATIONS. 


leasing  mechanism  which  permits  the  regular  operation  of  the 
inlet  valves  so  long  as  the  air  pressure  does  not  exceed  the 
normal.  When  this  pressure  is  exceeded  the  trip  on  the  suc- 
tion valves  is  released  and  the  valve  left  wide  open,  relieving 
the  compressor  of  its  load.     This  is  effected  by  a  loaded  plunger 


«ni^^ 


"0:^ 


f 


subject  to  the  air  pressure  which  acts  upon  a  set  of  knock- off 
cams,  in  action  similar  to  the  release  hook  of  the  Corliss  gear. 

The  combined  pressure  and  speed  regulator  of  this  company 
(Fig.  208)  consists  of  a  frictionless  plunger  loaded  with  a  spring 
and  weight,  and  a  centrifugal  governor.  These  two  mechanisms 
are  connected  to  a  floating  lever  in  such  a  manner  that  they 


AIR    COMPRESSORS    OF    THE    NORDIiERG    MFG.   COMPANY.      393 

can  act  independently  of  each  other  on  the  expansion  gear  of 
the  engine,  the  adjusting  rod  of  which  is  also  connected  to  the 
floating  lever.  The  centrifugal  governor  is  extremely  static, 
to  such  a  degree  that  the  speed  required  to  lift  it  to  its  highest 
position  is  four  times  that  necessary  to  just  raise  it  clear  of  the 


Fig.  20^.— the  unloading  device. 


sustaining  collar.  The  plunger  is  actuated  by  the  air  pressure, 
which  is  counteracted  principally  by  the  weight,  while  the 
spring  pressure  is  only  sufficient  to  produce  a  slightly  increas- 
ing resistance  as  the  plunger  is  depressed.  The  connection 
between  the  two  elements  of  regulation  and  the  expansion  gear 


394 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


■^Arip%^-'r-.-:  ^^ 


AIR   COMPRESSORS    OF   THE   NORDBERG    MFG.  COMPANY.      395 

is  such  that  a  rise  of  the  governor  (or  increase  of  engine  speed) 
and  an  increase  of  air  pressure  produce  the  same  effect,  viz., 
a  shorter  cut-off.  In  a  well-designed  compressor  the  mean 
effective  air  pressure,  and  consequently  the  mean  effective  steam 


Q    b 

<  z 


pressure,  is  practically  the  same  at  all  speeds,  and  the  point 
of  cut-off  is  therefore  fixed  and  independent  of  the  speed. 
Bearing  in  mind  this  fact,  the  action  of  the  governor  will  be 
readily  understood.     When  the  pressure  tends  to  drop,  due  to 


39^ 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


an  increased  consumption  of  air,  the  plunger  is  forced  higher 
up  into  its  barrel  by  the  action  of  the  spring  and  the  engine  is 
momentarily  given  more  steam,  which  causes  it  to  accelerate 


^^^^ 


Fig.  208.— combined  pressure  and  speed  regulator. 


its  motion.  The  acceleration  causes  the  governor  to  rise,  and 
thereby  shorten  the  cut-off,  until  it  reaches  such  a  height  that 
it  brings  the  cut-off  gear  back  to  about  its  original  position, 
when  the  speed  of  the  compressor  will  settle  down  to  that  cor- 


AIR    COMPRESSORS    OF   THE    NORDBERG    MFG.  COMPANY.      397 

responding  to  the  new  position  of  the  governor.  The  reverse 
action  takes  place  when  the  air  pressure  tends  to  rise.  A  per- 
fectly constant  air  pressure  can  thus  be  maintained  under  all 
variations  of  the  rate  of  consumption  of  air. 

Other  compressors  of  the  Nordberg  Company  are  illustrated 
in  Figs.  209  to  214  and  an  intercooler  in  Fig.  215. 


398 


COMPRESSED   AIR  AND    ITS   APPLICATIONS. 


O  V 

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AIR   COMPRESSORS    OF   THE    NORDBERG    MFG.  COMPANY.      399 


OS     -o 


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400 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


5     a 


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AIR   COMPRESSORS    OF   THE    NORDBERG    MFG.   COMPANY.       4OI 


o    -^ 


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402 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


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AIR    COMPRESSORS    OF   THE    NORDBERG    MFG.  COMPANY.      4O3 


2     3 


404 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


THE    GAS   AND     GASOLINE     ENGINE    IN    AIR    COMPRESSION. 

The  field  of  usefulness  of  compressed  air  is  already  large, 
and  is  continually  broadened  by  the  increasing  facilities  for  its 
production  by  simple  means  that  may  be  easily  transported  to  any 


needed  location.  This  has  been  found  in  the  adaptation  of  the 
gasoline  engine  for  power  and  its  combination  with  an  air  com- 
pressor. There  is  probably  nothing  so  economical,  within  its 
limits  of  power,  for  compressing  air  as  the  gasoline  engine ;  and 
certainly  no  means  so  easily  transported  to  any  required  loca- 


AIR    COMPRESSORS    OF    THE    GASOLINE    TVI'E. 


405 


tion  for  temporary  work.  In  the  vast  output  of  modern  steel 
construction  of  buildings  and  bridge-work,  compressed  air  now 
performs  a  vital  portion  of  the  work  of  assembling  such  struc- 
tures, and  has  found  its  great  aid  in  the  portable  air  compressor 


2   o 
9    ^ 


■^    S 


as  a  reliable  power  producer  for  operating  air  drills,  hammers 
for  riveting  and  chipping,  and  air  lifts. 

In  Fig.  216  is  illustrated  the  single-acting  air  compressor 
of  the  Fairbanks-Morse  Company,  with  engine  and  air  cylin- 
ders arranged  in  line  and  the  pistons  connected  by  a  yoke  and 


4o6 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


rods.     The  engine  is  of  the  four-cycle  type,  with  two  fly-wheels 
heavy  enough  to  carry  the  air  piston  over  a  second  stroke. 

Figs.     217    and    218     show    the     cross-connected     double- 
acting    air    compressor    and    gasoline    engine.       The    massive 


frames  of  engine  and  compressor  are  strongly  bolted  together 
so  as  to  make  three  rigid  bearings  for  the  crank  shaft,  which 
has  a  centre  crank  for  the  engine  and  an  outboard  crank  for  the 
compressor.     The  air  valves  are  of  the   removable  cage  type 


AIR    COMPRESSORS    OF    THE    KEROSENE-OIL   TYPE. 


407 


with  seating  springs.  The  engines  are  provided  with  electric 
and  tube  igniters,  and  a  self-starting  device  with  pump  and 
gasoline  charger,  which  is  a  most  essential  feature  in  a  gaso- 
line engine  having  a  fixed  load. 


A    KEROSENE-OIL   COMPRESSOR. 


The  lines  of  economy  are  rapidly  advancing  in  the  devices 
for  compressing  air,  and  kerosene  as  a  power  fuel  has  come  to 


Fig.  219.— kerosene-oil-actuated  air  compressor. 

the  front  in  the  Merrill  oil-actuated  air  compressor  (Fig.  219), 
which  is  a  self-contained  and  portable  power,  suited  for  all 
places  in  which  a  cheap  and  movable  power  is  requisite,  and 
weir  adapted  for  the  operation  of  pneumatic  tools  on  structural 
and  bridge  work.     For  the  production  of  air  power  for  oper- 


408  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

ating  pneumatic  pumping  systems  it  is  the  cheapest  and  most 
convenient  power  in  use,  save  some  special  conditions  of  water 
power.  These  air  pumps  operating  with  kerosene  oil  use  less 
than  one  pint  of  oil  per  horse  power  per  hour.  The  oil  is 
stored  in  the  base  of  the  engine,  is  supplied  to  the  vaporizer  by 
a  small  pump,  and  is  vaporized  by  the  heat  of  the  exhaust.  A 
blow  lamp  is  used  for  starting  the  vaporizer. 

COMBUSTION    AND    EXPLOSIONS    IN    COMPRESSOR    CYLINDERS, 
RECEIVERS,    AND    PIPE    LINES. 

Ignition  in  compressor  cylinders,  receivers,  and  air  pipes 
has  been  an  occasional  theme  of  discussion  among  engineers 
and  operators  of  compressed-air  plants,  with  sometimes  misgiv- 
ings in  regard  to  its  dangerous  conditions.  The  danger  has 
been  over-rated,  as  it  is  well  known  that  the  explosive  power  of 
hydrocarbon  vapor  and  air  mixtures,  even  under  the  compres- 
sion pressures,  of  gas  and  oil-vapor  engines  seldom  exceeds  300 
pounds  per  square  inch.  Such  being  the  case,  most  air  receiv- 
ers have  a  limit  of  strength  equal  to  this  or  more,  so  that  as  a 
precaution  receivers  that  are  used  for  pressures  of  any  amount 
should  have  a  tensile  tested  strength  of  at  least  five  times  the 
working  pressure,  and  six  times  may  be  considered  a  safe  test. 
As  to  the  conditions  of  safety  and  danger,  the  following  re- 
marks from  that  valued  journal.  Compressed  Air,  are  pertinent 
to  the  question  in  all  its  bearings: 

"  Compressed  air  claims  to  be  and  is  a  safe  power.  Occa- 
sionally we  hear  of  a  case  of  firing,  which  to  some  may  appear 
to  be  a  serious  objection  to  the  use  of  air ;  but  if  the  causes  are 
known  and  understood  and  due  care  is  observed,  firing  becomes 
merely  a  matter  of  carelessness.  .  .  .  Compressed  air  is  not 
inflammable,  but  during  compression  by  mechanical  means  it  is 
found  advisable  to  use  oil,  and  this  oil,  or  the  gases  from  it,  are 
the  sources  of  combustion.  In  most  cases  firing  may  be  traced 
to  the  use  of  poor  oil,  but  in  others  too  much  oil  sometimes 


COMBUSTION   AND    EXPLOSIONS.  4O9 

causes  ignition.  It  is  a  common  mistake  of  engineers  in  charge 
of  compressors  to  feed  oil  too  rapidly  to  the  air  cylinder.  It  is 
simply  necessary  to  supply  oil  enough  to  keep  the  interior  of 
the  cylinder  and  the  moving  parts  moistened.  Where  steam  is 
used  there  is  a  tendency  to  cut  away  the  oil,  hence  engineers 
grow  accustomed  to  feeding  a  larger  supply  than  is  required  in 
an  air  cylinder.  There  is  nothing  to  cut  or  absorb  the  oil  in 
the  air  end ;  in  fact,  it  is  only  after  a  considerable  lapse  of  time 
that  oil  can  get  away  when  fed  into  the  cylinder.  There  is  no 
washing  tendency  as  with  steam,  and  a  drop  now  and  then  is 
all  that  is  required  to  keep  the  parts  lubricated.  Where  too 
much  oil  is  used  there  is  a  gradual  accumulation  of  carbon, 
which  interferes  with  the  free  movement  of  the  valves  and 
which  chokes  the  passages,  so  that  a  high  temperature  may  for 
a  moment  be  formed  and  ignition  follow.  It  is  well  to  get  the 
best  oil,  and  to  use  but  little  of  it. 

"  There  are  cases  where  firing  has  arisen  from  the  introduc- 
tion of  kerosene  or  naphtha  into  the  air  cylinder  for  the  purpose 
of  cleaning  the  valves  and  cutting  away  the  carbon  deposits. 
Every  engineer  knows  how  easily  he  may  clean  his  hands  by 
washing  them  in  kerosene ;  and  as  this  oil  is  usually  available, 
we  have  seen  men  introduce  it  into  the  air  cylinder  through  a 
squirt-can  at  the  inlet  valve.  This  is  a  very  effective  way  of 
cleaning  valves  and  pipes,  but  it  is  a  source  of  danger,  and 
should  be  absolutely  forbidden.  High-grade  lubricating  oils 
are  carefully  freed  of  all  traces  of  benzine,  naphtha,  kerosene, 
and  other  light  and  volatile  distillates.  The  inflammability  of 
the  latter  is  so  acute  that  it  is  a  dangerous  experiment  to  intro- 
duce anything  of  this  kind  into  an  air  cylinder;  and  if  any  of 
our  readers  have  had  an  explosion  in  a  case  where  the  engineer 
uses  kerosene,  it  may  be  traced  to  this  source.  Closed  inlet 
passages  leading  to  the  air  cylinder  through  which  the  free  air 
is  drawn  from  outside  the  building  have  many  advantages,  but 
one  seldom  thought  of  is  that  they  interfere  with  the  tendency 
of  the  engineer  to  squirt  kerosene  into  the  cylinder. 


4IO  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

"  wSoft-soap  and  water  is  the  best  cleanser  for  the  air  cylin- 
der, and  it  is  recommended  even  in  cases  where  the  best  oil  is 
used.  Long  service  will  result  in  more  or  less  accumulation  of 
carbon ;  hence  it  is  advised  that  engineers,  once  or  twice  a 
week  or  oftener  if  necessary,  fill  the  oil  cup  with  soft-soap  and 
water  and  feed  it  into  the  cylinder  as  the  oil  is  fed. 

"  Ignition  in  compressed-air  discharge  pipes  and  passages  is 
not  uncommon.  At  times  this  ignition  is  in  the  nature  of  an 
explosion.  Two  air  receivers  were  blown  up  during  the  con- 
struction of  the  New  York  Aqueduct ;  in  one  case  the  engine 
room  was  destroyed  by  fire  resulting  from  this  explosion.  We 
have  also  records  of  two  other  cases  where  spontaneous  explo- 
sions in  the  air  receiver  have  resulted  in  the  destruction  of  the 
engine  room  by  fire.  Other  instances  occur  where  ignition 
takes  place  near  the  air  compressor,  the  pipes  becoming  red- 
hot  at  the  joints.  This  ignition  has  been  known  to  extend  into 
the  air  receiver,  and  in  one  instance  the  flames  were  carried 
down  into  the  mine  by  the  compressed  air. 

"  In  all  such  cases  large  volumes  of  compressed  air  were 
used.  It  is  plain  that  the  cause  of  the  explosion  or  ignition  is 
an  increase  of  temperature  above  the  flash  point  of  the  oil 
which  is  used  to  lubricate  the  compressor.  A  thick  or  cheap 
grade  of  cylinder  oil  should  never  be  used  in  an  air  compressor. 
Thin  oil  which  has  a  high  flash  point,  and  which  is  as  free  from 
carbon  as  conditions  of  lubrication  will  admit,  is  the  best  oil. 
A  correspondent  calls  attention  to  explosions  v.'here  the  flash 
point  of  the  oil  is  554°  F.,  and  ignition  point  606°  F.  We 
know  of  an  instance  where  ignition  took  place  with  oil  which 
had  a  flash  point  of  S/S""  F.,  ignition  point  625°  F.  Conditions 
were  similar  to  those  mentioned  by  our  correspondent,  that  is, 
the  air  was  compressed  to  about  60  pounds  per  square  inch 
gauge  pressure.  If  the  temperature  of  the  air  before  admission 
to  the  compressor  is  60°  F.,  and  it  is  compressed  to  58.8 
pounds  gauge  pressure,  the  final  temperature,  where  no  cooling 
is  used  during  compression,  will  be  369.4°  F.,  or  a  total  increase 


COMBUSTION   AND    EXPLOSIONS.  4  II 

of  309.4°.  If  air  is  admitted  at  60°  F.,  is  compressed  without 
cooling  to  73.5  pounds  gauge  pressure,  the  final  temperature 
will  be  414.5°  F.,  and  the  total  increase  of  temperature  354.5°. 
Under  such  circumstances  the  question  naturally  arises,  How  is 
it  possible  when  using  oil  with  an  ignition  point  of  over  600° 
to  get  an  ignition,  especially  as  water  jackets  and  other  methods 
of  cooling  are  used  which  should  reduce  the  final  temperature? 
The  figures  are  also  based  on  dry  air,  which  increases  in  tem- 
perature during  compression  to  a  greater  degree  than  moist  air, 
and  it  is  known  that  air  that  is  used  in  compressors  is  never 
very  dry.  The  theoretical  figures  show  that  in  order  to  get 
ignition  with  the  oil  mentioned,  the  gauge  pressure  should  be 
about  200  pounds  per  square  inch,  where  no  cooling  takes  place. 
"  It  is  plain  that  there  must  be  an  increase  of  temperature 
or  ignition  would  not  take  place.  This  increase  of  temperature 
may  result  either  from  an  increase  of  pressure  which  is  not 
recorded  on  the  gauge,  or  there  may  be  an  increase  of  temper- 
ature without  a  corresponding  increase  of  pressure.  Take  the 
first  instance,  and  it  is  not  difficult  to  understand  that  an  air 
compressor  might  deposit  carbon  from  the  oil  in  the  discharge 
passages  or  discharge  pipes  which  in  the  course  of  time  will 
accumulate  and  constrict  the  passages  so  that  they  do  not  freely 
pass  the  volume  of  air  delivered  by  the  compressor,  hence  a 
momentary  increase  of  pressure  might  exist  in  the  cylinder 
heads  or  in  the  discharge  pipe  which  leads  from  the  air  cylin- 
der to  the  receiver ;  this  momentary  increase  of  pressure  would 
surely  carry  with  it  an  increase  of  temperature  which  might 
exceed  the  ignition  point  of  the  oil.  A  badly  designed  com- 
pressor with  inefficient  discharge  passages  might  produce  this 
trouble.  Too  small  a  discharge  pipe  or  too  many  angles  in  dis- 
charge pipes  might  also  tend  to  produce  explosions.  But  we 
have  known  instances  where  ignition  has  occurred  in  a  well- 
designed  system,  hence  we  must  look  for  other  causes.  In  our 
judgment  the  majority  of  cases  may  be  traced  to  an  increase 
of  temperature  without  an  increase  of  pressure ;  this  increase  of 


412  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

temperature  can  be  excessive  only  when  the  temperature  of 
the  incoming  air  is  excessive.  A  hot  engine-room  from  which 
air  is  drawn  into  the  cylinder  is  a  bad  condition.  We  have 
known  cases  where  the  incoming  air  was  drawn  from  the  neigh- 
borhood of  the  boiler,  the  temperature  being  close  to  150°  F. 
This  means,  of  course,  that  if  the  total  increase  of  temperature 
when  air  is  compressed  to  73.5  pounds  gauge  pressure  is  354.5°, 
the  temperature  of  the  initial  air  should  be  added  to  this  figure, 
and  that  the  final  temperature  might  be  504.5°. 

"  But  we  have  known  ignition  to  take  place  when  the  tem- 
perature of  the  incoming  air  was  normal,  when  the  discharge 
passages  and  pipes  were  free  and  of  ample  area,  hence  we  must 
look  for  some  other  cause.  The  only  possible  explanation  is 
that  the  temperature  of  the  incoming  air  is  made  excessive  by 
the  sticking  of  one  or  more  of  the  discharge  valves,  thus  letting 
some  of  the  hot  compressed  air  back  into  the  cylinder  to  influ- 
ence the  temperature  before  compression.  When  a  piston  of 
an  air  compressor  has  forced  a  cylinder  volume  of  air  through 
the  discharge  valve,  and.  when  this  piston  has  its  direction  of 
movement  reversed,  there  will  immediately  be  a  tendency  of  the 
air  just  compressed  and  discharged  to  return  to  the  cylinder. 
In  this  it  is  checked  by  the  discharge  valve,  but  through  long 
and  constant  use  these  discharge  valves  become  encrusted  with 
carbon  and  are  not  free  to  move,  hence  there  may  be  a  moment 
when  one  of  these  valves  sticks,  or  it  may  not  seat  properly;  in 
either  case  there  will  be  some  hot  compressed  air  in  the  cylin- 
der when  the  piston  starts  on  its  return  stroke  of  compression ; 
the  air  ma}-  have  lost  its  pressure,  but  not  its  temperature,  and 
it  is  not  dilficult  to  understand  a  leaky  discharge  valve  letting 
enough  air  back  into  the  cylinder  to  increase  the  initial  tem- 
perature to  two  or  three  hundred  degrees.  If  so,  and  we  are 
compressing  air  to  73.5  pounds  gauge  pressure,  we  have  say 
300°  temperature  in  the  free  air  before  compression,  and  as 
the  increase  is  354.5°,  the  resulting  temperature  might  be 
654.5°. 


COMBUSTION    AND    EXPLOSIONS.  413 

"  As  a  remedy  \xe  would  suggest  more  care  in  selecting  the 
best  air  compressor  and  in  frequent  cleaning  of  the  discharge 
valves  and  passages.  The  best  air  compressors  are  built  so 
that  the  discharge  valves  may  be  readily  removed ;  these  valves 
should  be  cleaned  regularly  once  a  week  by  the  engineer,  who 
should  make  sure  that  they  fit  properly.  It  is  impossible  to 
get  good  lubricating  oil  that  is  free  from  carbon,  hence  there 
w'ill  always  be  more  or  less  carbon  deposited  on  the  discharge 
valves,  but  this  must  not  be  allowed  to  accumulate. 

"  Intercoolers  between  air  cylinders  and  after-coolers  be- 
tween final  cylinder  and  receiver  are  also  recommended.  The 
best  intercoolers  are  made  of  nests  of  brass  tubes,  the  air  pass- 
ing around  the  tubes  and  the  w'ater  through  them,  hence  there 
is  a  thorough  splitting  up  of  the  air  and  efficient  cooling.  One 
of  these  coolers  located  in  the  discharge  pipe  will  absolutely 
prevent  the  passage  of  flame  and  will  insure  the  protection  of 
the  mine  against  fire  even  though  there  be  ignition  at  or  near 
the  air  cylinder." 


Chapter  XXII. 


•     COMPRESSED  AIR  IN 
MINING  AND  QUARRYING 


COMPRESSED    AIR    IN    MINING   AND   QUARRYING. 


The  rock  drill  as  a  self-acting  power  machine  for  rock-drill- 
ing is  the  outcome  of  the  past  half-century ;  the  first  self-oper- 
ating percussion  rock  drill  dates  from  1849,  under  the  Couch 
patent;  since  which  time 
Fowle,  Burleigh,  Inger- 
soll,  Wood,  Githens, 
Rand,  and  Sergeant  have 
improved  on  its  design 
and  brought  its  construc- 
tion to  the  present  per- 
fect action.  At  this  time 
more  than  a  hundred 
thousand  rock  drills  attest 
their  usefulness  in  min- 
ing, tunnelling,  and  quar- 
rying throughout  the  civ- 
ilized world. 

Fig.  221  is  a  section 
of  the  Ingersoll  drill.  A, 
the  shell ;  B,  piston  with 
rotating  device ;  R,  air 
chest ;  T,  bolt  that  holds 
the  heads  of  the  air  chest 
and  on  which  the  balanced 
piston  valve  slides,  and  which  is  thrown  by  small  air  ports 
opened  by  the  drill  piston  at  the  end  of  its  stroke. 

Other  models   of  drill  valves   are   made   by  the   Ingersoll- 
Sergeant  Drill  Company,  the  invention  of  Mr.  Henry  C.  Ser- 
geant, among  which  are  the  tappet  valve  for  a  rock  drill.     The 
27 


Fig.  220.— ihe  new  ingersoll. 
On  universal  tripod. 


4i8 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


ports  are  radial  and  flat,  and  are  opened  and  closed  by  the 
swing  of  the  valve  on  its  centre.  The  valve  is  thrown  by  the 
shoulders  on  the  piston  striking  the  valve  arms. 


Fig.  221.— section  of  the  ingersoll. 


Another  improvement  is  shown  in  Fig.  223,  being  an  arc 
tappet  valve  motion,  for  a  rock  drill.  The  valve  is  moved  on 
a  circle  radial  with  the  tappet  centre,  and  is  thrown  by  the 
tappet-arm  contact  with  the  shoulders  on  the  piston. 

Another  rock  drill  of  this  company  is  the  "  vSergeant  drill," 
having  a  piston  valve  as  in  the  Ingersoll  model,  which  is  thrown 


Fig.  222.— tappet  \alve. 


Fig.  223.— akc  tappet  valve. 


by  an  auxiliary  arc  valve  or  ported  sector  that  opens  the  small 
ports  alternately  behind  the  piston  valve.  The  sector  is  thrown 
by  contact  with  the  shoulders  of  the  central  recess  in  the  drill 
piston.  It  is  the  trigger  of  the  main  or  piston  valve,  and  opens 
or  closes  the  air  passages  to  the  piston  valve  alternately.     It  is 


Fig.  224.— auxiliary  arc  valve. 


so  light  that  it  is  quickly  and  positively  moved  by  the  passing 
of  the  piston  shoulder  and  held  in  position  to  near  the  end  of 
the  drill  piston  stroke. 


COMPRESSED    AIR    IN    MINING    AND    QUARRYING.  419 


Types  of  Air  and  Steam  Rock  Drills  of  the  Ingersoll- 
Sergeant  Drill  Co. 


Fig.   225.  — the  SliRGEANT   KOCK   DRILL. 

In  sizes  2,  2%,  3,  sJ^,  and  sJ^-inch  diameter  of  pistons.     Stroke,  4%,  6yi,  and  7  inch. 


420 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Types  of  Air  and  Steam  Rock  Drills  of  the  Ingersoll- 
vSer(;eant  Drill  Co. 


Fig.  226.— the  ixgersoll  eclipse  drill. 

Mounted  on  Sergeant  universal  joint  tripod.     i%,  -2%,  2^,  3,  3^^,  ^%,  4'A,  and  5-inch  diameter 

of  piston.    4  to  8-inch  stroke. 


compressed  air  in  mining  and  quarrying.  42 1 

Types  of  Air  and  Steam  Rock  Drills  of  the  Ingersoll- 
Sergeant  Drill  Co. 


Fig.  227.— the  ingeksoll  automatic  fked  drill. 

As  the  piston  approaches  the  front  head  in  cutting-,  it  strikes  a  knuckle  joint  which  turns 
a  nut  on  the  feed  screw.  The  hirgest  rock  drill  made  ;  4K  and  5-inch  diameter  ;  S-inch  stroke. 
Its  special  application  is  in  submarine  work. 


422 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


Types  of  Air  and  Steam  Rock  Drills  of  the  Ingersoll- 
Sergeant  Drill  Co. 


Fig.  228.— 1  he  arc  valve  tappet  dkili.. 

A  positive  valve  motion  by  direct  contact  of  the  tappet  with  the  piston.     Made  in  the  usual 
sizes  of  the  Ingersoll-Sergeant  Drill  Company. 


COMPRESSED    AIR    IN    MINING   AND    QUARRYING. 


423 


THE    BAR    CHANNELLER. 

In  the  bar  channeller  has  been  found  one  of  the  most  useful 
of  the  air-driven  machines  for  quarrying  dimension  stone  for 
building.  It  has  been  greatly  developed  and  improved  of  late 
years.  One  of  its  novelties  is  an  independent  air  motor  that 
traverses  the  drill  forward  and  back  along  the  bars  at  regulated 


Fig.  229.— the  channelling  .\lachine. 


speed,  thus  enabling  long  channel  cuts  to  be  made  quickly  and 
with  accuracy.  This  with  the  quarry  bar  and  gadder  are  es- 
sential features  in  the  operation  of  marble  and  slate  quarries. 


COAL    CUTTING   BY    COMPRESSED    AIR. 

The  past  decade  has  developed  great  progress  in  the  mining 
of  coal  in  Europe  and  the  United  States,  by  the  introduction  of 
compressed  air  for  many  of  the  operations  that  before  were 
tediously  wrought  by  hand.  The  hand  coal  pick  has  been 
largely  displaced  by  the  introduction  of  the  compressed  air  pick 
or  coal-cutting  machine,  which  is  essentially  a  rock  drill  on 
wheels  with  a  long  sharp  blade,  by  which  the  wall  face  of  a 
coal  seam  is  under-cut  alonor  the  bottom  of  its  face  and  shear- 


424 


COMPRESSED    AIR   AND    ITS    APPLICATIONS, 


cut  in  vertical  seams  from  top  to  bottom  by  merely  changing 
the    small   wheels  to   larger  ones  to  give  the  pick  a  vertical 


-^^^^^ 


Fig.  230.— compressed  air  coal-cutting  machine. 

range.  By  the  use  of  the  coal-cutter  a  miner's  work  per  shift 
is  increased  from  four  to  six  times  over  old  methods. 

Fig.  230  is  a  sectional  view  of  the  IngersoU-Sergeant  Coal- 
Cutting  Machine  with  its  double  piston  valve  movement  in 
which  the  alternating  strokes  of  the  valves  are  made  automatic 
by  the  cross  connections  of  their  ports,  thus  alternating  the 
stroke  of  the  main  pick  piston. 

Fig.  231  shows  the  position  of  the  coal-cutter  on  an  inclined 


Fig.  231.— ingersoll-sergeant  coal-cutter. 

platform  and  the  position  of  the  operator  ready  for  making  an 
under-cut  in  a  coal  face. 


COMPRESSED    AIR    FOR    INGERSOLL-SERGEANT    ROCK    DRILLS    AND 

COAL-CUTTERS. 

The  following  table  is  intended  to  show  at  a  glance  the  ap- 
proximate quantity  or  volume  of  free  air  required  for  operating 
rock  drills  and  coal-cutters,  the  air  being  delivered  to  the  ma- 
chines at  60  pounds  pressure. 


COMPRESSED    AIR   IN    MINING   AND    QUARRYING. 


425 


As  applied  to  rock  drills,  these  figures  are  necessarily  ap- 
proximate only,  owing  to  the  varying  conditions  under  which 
such  work  is  performed  ;  but  they  will  be  found  to  apply  closely 
to  average  conditions  in  rock  of  moderate  hardness.  A  liberal 
allowance  has  been  made  above  the  actual  requirements  of  new 
machines,  to  provide  for  wear,  etc.,  but  no  allowance  is  made 
for  leaky  pipe,  as  this  should  not  be  permitted  to  exist.  In 
soft  material  the  actual  drilling  time  is  short,  and  more  drills 
can  be  run  with  a  given  size  compressor  than  where  the  mate- 


FlG.    232.— REAK    VIEW,   COAL-CUTTER. 

rial  is  hard  and  the  drills  running  continuously  for  a  longer 
period. 

In  tunnel  work  in  hard  rock,  where  a  high  air  pressure  is 
carried  to  insure  rapid  progress,  experienced  contractors  have 
found  it  profitable  to  provide  compressor  capacity  in  excess  of 
the  usual  requirements  by  25  to  50  per  cent. 

For  coal-cutters,  the  figures  given  are  liberal,  and  more 
machines  can  probably  be  added  where  a  large  plant  is  in  oper- 
ation ;  but  it  should  always  be  remembered  that  it  is  better 
economy  to  provide  a  large  compressor  and  run  it  slowly,  rather 
than  a  small  one  that  has  to  be  driven  to  its  full  capacity.     This 


426 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


fact  is  recognized  by  the  best  engineers,  and  it  applies  more 
particularly  to  a  compressor  than  to  an  engine  or  boiler. 

The  capacities  in  this  table  are  based  on  60  pounds  air  press- 
ure; if  75  pounds  is  used,  one-fifth  more  volume  should  be 
added  to  the  volume  stated  in  the  table  ;  if  90  pounds,  two-fifths 
should  be  added. 


TABLE   XL. — Cubic  Feet  of  Free  Air  per  Minute  Required  to  Run  from 
One  to  Forty  Ingersoll-Sergeant  Drills  with  Sixty  Pounds  Pressure. 


Rock  Drills— Sizes. 

Coalcutters. 

A 
2  inch. 

B 
■zyi.  inch. 

C 
2j^  inch 

D  . 
.3  inch.' 

E 
3:^  inch. 

F 
■i%,  inch. 

G 
4J^  inch. 

H. 
5  inch. 

zVi  inch. 

4  inch. 

I 

65 

70 

95 

IIO 

115 

125 

140 

165 

70 

93 

2 

IIO 

120 

169 

19D 

200 

230 

250 

280 

140 

186 

3 

156 

174 

234. 

279 

294 

333 

360 

405 

210 

279 

4 

196 

220 

304 

356 

.      372 

428 

460 

524 

280 

372 

s 

230 

260 

370*" 

.425 

■-    445 

510 

555 

635 

350 

465 

6 

264 

294 

426 

..   486  • 

.       516 

588' 

642 

738 

420 

558 

7 

294 

329 

476 

\    546 

-■     581 

658 

721 

826 

490 

651 

8 

320 

360 

520 

600 

640 

720 

800 

920 

560 

744 

9 

360 

405 

585 

675 

•720 

810 

900 

1,035 

630 

837 

10 

400 

450 

650 

750 

.  800 

900 

1,000 

1,150 

700 

930 

12 

480 

540 

780 

900 

960 

1,080 

1,200 

1,380 

840 

1, 116 

15 

675 

975 

1,125 

1,200 

1,350 

1,500 

1,725 

1,050 

1,395 

20 

1,300 

1,500 

1,600 

1,800 

2,000 

2,300 

1,400 

1,860 

25 

1,625 

1,875 

2,000 

2,250 

2,500 

2,775 

1,750 

2.325 

30 

1,950 

2,250 

2,400 

2,7-0 

3.000 

3.450 

2,100 

2,790 

40 

2,600 

3,000 

3,200 

3,600 

4,000 

4,600 

2,800 

3.720 

The  operation  of  the  compressed-air  coal  cutter  depends 
upon  the  automatic  action  of  a  double  piston  valve  in  a  valve 
chest  immediately  over  the  cylinder.  The  action  of  the  valve 
pistons  is  alternating,  each  piston  opening  ports  for  its  opposite 
valve,  one  of  which  is  the  supplementary  piston. 

The  illustrations  will  serve  to  give  a  correct  idea  of  the  ap- 
pearance of  the  pick  machine.  It  is  mounted  on  wheels  16  to 
20  inches  in  diameter,  according  to  the  requirements ;  weighs 
from  500  to  750  pounds,  and  is  easily  moved  from  one  place  to 
another,  the  time  consumed  in  moving  from  room  to  room  of 
average  length,  including  loading  and  unloading,  being  about 
ten  minutes.  In  operation  the  machine  is  placed  on  a  platform 
made  of  2-inch  pine,  about  8  feet  long  and  3  feet  wide,  which 


COMPRESSED    AIR    IN    MINING   AND    QUARRYING 


427 


is  so  inclined  toward  the  face  by  means  of  a  trestle  under  the 
outer  end  that  the  recoil  of  the  machine  is  neutralized  by  grav- 
ity and  feeds  down  to  the  coal.     The  method  of  mining  is  as 


Fig.  233.— the  CHICAGO  rock  drill. 
The  Chicago  Pneumatic  Tool  Co.,  Chicago,  111.,  and  New  York  City. 

follows :  The  runner  sits  on  the  platform  behind  the  machine, 
which  he  holds  by  the  handles ;  the  pick  is  shot  against  the 
coal  by  means  of  compressed  air  at  a  pressure  of  from  40  to  90 


428 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


pounds,  Striking  with  a  force  and  speed  which  can  readily  be 
adjusted  to  range  from  i6o  to  250  blows  per  minute,  at  a  force 
per  blow  at  from  5  to  1,500  pounds.  The  runner  uses  a  block 
attached  to  his  shoe  by  a  strap  to  chock  the  wheels  of  the  ma- 
chine against  the  recoil. 


ROCK    DRILLS    OF   THE    CHICAGO    PNEUMATIC    TOOL    COMPANY. 

The  Chicago  reciprocating  rock  drill  is  an  improvement  on 
the  old  style  rock  drill ;    it  is  equipped  with  an  auxiliary  valve, 

which  acts  as  a  controller 
for  the  main  valve,  thus 
insuring  a  perfect  valve 
movement.  It  is  used  in 
quarries,  for  excavating 
and  tunnelling,  and  in 
shaft  and  mme  work. 

The  Chicago  rock  drill 
is  a  combination  of  a 
pneumatic  hammer  and  a 
pneumatic  drill.  In  the 
cylinder  of  the  hammer  is 
set  a  drill  bit  made  of 
grooved  steel  Jg  inch  in 
diameter,  in  any  desired 
length.  The  chuck  is  cut 
out  to  fit  a  cross-section 
of  the  drill  bit,  so  that 
the  same  can  be  set  in 
the  hammer  socket 
loosely,  requiring  no  set 
screws,  bolts,  or  pins  to 
hold  it  in  place.  This 
saves  much  time  and  annoyance.  A  tube  encases  the  drill  bit, 
the  tube  encircled  by  a  spiral,  which,  when  the  drill  bit  revolves, 


Fig.  234.— CHICAGO  rock  dkill. 
Hammer  type. 


COMPRESSED    AIR   IN    MINING   AND    QUARRYING. 


429 


serves  to  remove  from  the  hole,  as  the  drill  advances,  all  the 
cuttings  of  rock  and  other  material,  much  after  the  order  of  the 
auger  bit.  There  are  four  tongues  riveted  to  the  internal  diam- 
eter of  the  casing,  fitting  four  grooves  in  the  bit,  compelling  it 
to  rotate  simultaneously  with  the  drill. 


■Mi 


Fig.   235.— XO.   2^/i   DRILL  ON  TRIPOD. 


ROCK    DRILLS    OF   THE    McKIERNAN    DRILL    COMPANY, 
NEW    YORK    CITY. 

The  drills  of  this  company  are  made  in  nine  sizes,  viz. :  2 
in.,  2i-  in.,  2^  in.,  3  in.,  31/8  in.,  ^'A  i^.,  3t  in.,  S-A  in.,  and 
5  in. ;  the  last  size  being  a  specially  arranged  drill  for  sub- 
marine drilling. 


430  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

They  are  substantially  constructed  on  the  lines  of  the  ex- 
pired Ingersoll  patents,  with  the  usual  spiral  bar  with  ratchet 
and  pawl  rotation,  and  provided  with  a  release  movement  for 
obviating  possibility  of  breakage.  The  cylinder  heads  are  held 
by  strong  helical  springs  of  steel  braced  by  through  rods  to  lugs 
at  the  lower  end  of  the  cylinder,  thus  relieving  the  machine 

from  jar  by  the  piston 
striking  the  cylinder 
head. 

One  of  the  essential 

features  of  this  rock  drill 

is   the  valve,    on   which 

J     .  depends    the    action    of 

^^P^  the  drill.     The  valve  as 

FIG.  236.-THE  pisioN  vALvt.  shown   in   the   cut  is   of 

a  four-part  piston  type, 
turned  from  solid  tool  steel,  has  a  perfectly  balanced  motion  and 
moves  automatcially,  having  no  mechanical  connection  with  the 
piston ;  it  being  operated  by  air  ports  opened  and  closed  by  the 
alternating  movement  of  the  drill  piston.  An  annular  recess  at 
the  central  part  of  the  piston  opens  an  air  port  for  pressure  and 
exhaust  at  the  ends  of  the  piston  valve.  The  air  pressure  in 
the  valve  chest  is  between  each  of  the  ends  and  central  discs  of 
the  valve,  while  the  exhaust  takes  place  between  the  central  discs. 
Thus  the  valve  is  perfectly  balanced  and  only  requires  its  fric- 
tion to  be  overcome  b}'  the  alternating  air  pressure  on  the  ends. 
The  submarine  air  or  steam  rock  drill  of  this  company  has  a 
cylinder  of  5 -inch  diameter,  8i-inch  stroke,  and  for  the  purpose 
of  submarine  drilling  is  mounted  upon  a  wooden  slide  or  a 
special  frame  to  give  it  a  long  reach.  The  whole  apparatus  is 
mounted  on  a  spud  platform,  or  a  heavy  scow,  and  sometimes 
both  when  the  boiler  and  air  compressor  are  carried  on  the 
scow.  In  this  way  the  drill  has  a  more  steady  position  on  the 
spud  frame,  and  is  readily  moved  to  new  positions. 


COMPRESSED    AIR   IN    MINING   AND    QUARRYING. 


431 


ROCK    DRILLS    OF    THE    PHILLIPS    ROCK    DRILL   COMPANY, 
PHILADELPHIA,    PA. 

The  "Badger"  drill 
is  the  trade  name  of  the 
rock  drills  made  by  this 
company.  The  "  New 
Badger "  is  their  latest 
improvement. 

Its  general  construc- 
tion follows  the  lines  of 
the  best  types.  The 
blow  of  the  drill  is  iin- 
cushioned,  and  all  the 
energy  put  into  the  pis- 
ton, less  that  due  to  the 
friction  of  the  parts,  is 
expended  at  the  cut- 
ting edge  of  the  bit. 
The  valve  is  of  the  spool 
or  piston  type,  operated  by  air  ports  at  each  end  alternately 
opened  by  the  recess  in  the  drill  piston  near  the  ends  of  its  stroke. 

In   Fig.  239  is   shown   the   "New   Badger"  drill  on   tripod 


-THIC   BADGER   DKILL. 


Fig.  238.— longitudinal  section  of  the  drill. 
Showing  the  figured  parts  which  are  named  in  their  catalogue. 


+32 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

working  close  to  the  side  face 
of  a  rock  wall,  one  of  the 
most  inconvenient  positions 
for  operating  a  rock  drill. 


Fig.  239.— the  "new  badger." 
Working  close  to  side  face. 


THE  NEW  LEYNER  COMPRESSED-AIR 
ROCK  DRILL.  J.  GEORGE  LEYNER, 
DENVER,    COLO. 


This  is  a  pneumatic  or  air  drill, 
for  drilling  rock  or  ore  in  mines, 
tunnels,  and  quarries.  It  is  unlike 
the  type  of  rock  drills  that  have  been 
in  use  for  nearly  forty  years,  es- 
pecially in  this,  that  the  steel  is  en- 
tirely disconnected  from  the  piston. 
That  is  to  say,  the  steel,  instead  of 

being  plunged  by  the  piston  against  the  rock,  is  struck  by  the 
piston  and  driven  into  the  rock. 

A  hardened  steel  tapered  pin  in  the  front  end  of  the  piston 


Fig.   240.— section   of  the  levner 
rock  dkill. 


COMPRESSED-AIR    IN    MINING   AND    QUARRYING.  433 

Strikes  the  hardened  end  of  the  shank  of  the  drill  steel.  The 
weight  of  the  piston  is  but  a  little  more  than  one-fourth  of  the 
■weight  of  the  piston  of  an  ordinary  drill,  but  its  velocity  is 
about  four  times  as  great. 

The  steels  used  for  drilling  are  hollow.  A  small  steel  tank 
is  filled  with  water  and  connected  to  the  air  line  to  obtain  press- 
ure to  carry  the  wa- 
ter to  and  through 
the  drill.  This  tank 
is  connected  by 
means  of  a  hose  to  a 
suitable  connection 
on  the  back  of  the 
machine.  A  steel 
tube  passes  from  this 
water  connection 
through  the  machine 
and  into  the  hollow 
drilling  steel. 

A  needle  valve 
fitted  to  the  machine 
gives  the  operator 
perfect  control  of  the 
water  supply. 

Through  a  valve 
in  front  of  the  chest 
air  is  admitted  into 
the  front  of  the  cyl- 
inder, passes  out  through  the  steel,  and  is  discharged  from 
the  bit  into  the  hole  being  drilled,  thus  expelling  the  cuttings. 
By  turning  the  water  valve,  the  operator  mingles  a  spray  of 
water  with  the  compressed  air,  so  that  the  cuttings  expelled 
from  the  hole  are  free  from  dust. 

The  Leyner  drill  is  made  in  two  sizes,  viz. :  2|-inch  diame- 
ter of  piston,  whole  weight  of  drill   115  pounds;   3-inch  diame- 


FlG.   241.— LEYNER  ROCK  DRILL  ON  COLUMN. 


434 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


ter  of  piston,  whole  weight  165  pounds;  ready  for  mounting  on 
tripod  or  column. 


ROCK    DRILLS    OF   THE    RAND    DRILL    COMPANY,    NEW  YORK    CITY. 

Fig.  242  represents  "the  general  form  of  the  little  Giant 
Rock  drill,  and  Fig.  243  the  detail  of  the  valve  gear  and  rotat- 
ing device  in  section. 

The  valve  of  the  Little  Giant  drill  is  a  plain  slide-valve,  al- 
ways thrown  in  the  same 
direction  in  which  the 
piston  is  moving.  The 
opening  and  closing  is 
effected  in  a  positive 
manner. 

A  three-arm  rocker, 
or  lever,  operates  the 
valve  and  is  held  in 
place  by  a  pin  ;  the  rock- 
er is  placed  in  a  recess 
of  the  cylinder,  between 
the  ends  of  a  double- 
headed  piston,  and  its 
upper  arm,  or  head,  en- 
gages into  the  valve  ;  as 
the  piston  reciprocates 
it  shoves  the  rocker  in  the  direction  in  which  it  is  going  and 
thus  moves  the  valve  with  it. 

Fig.  244  represents  the  piston  or  spool  valve  of  the  Slug- 
ger air  drill.  It  is  a  three-part  spool,  and  is  operated  by  the 
opening  and  closing  of  small  ports  at  the  terminal  strokes  of 
the  drill  piston,  and  is  stopped  by  steel  spools  abutting  against 
soft  elastic  buffers. 

The  Slugger  drill  is  made  in  five  sizes  from  2^  to  3^  inch 
diameter,  and  from  6}{  to  /:■■{  inch  stroke.     These  drills  have 


Fig.  242.— the  litile  giant  kock  drill, 


COMPRESSED   AIR    IX    MIXING   AND    QUARRYIXG. 


435 


the  delayed  action  of  the  valve  at  the  striking  end  of  the 
stroke,  whereby  the  air  or  steam  is  not  admitted  to  the  front  of 
the  piston  until  the  blow  is  struck.  The  compressed  air  and 
steam  rock  drills  are  essentially  alike  in  action  and  have  a  good 
record  in  mining,  tunnelling,  and  quarry  work. 


Fig.  243.— valve  gear  and  rotating  device 
Of  the  Little  Giant  rock  drill. 

We  give  herewith  a  table  of  cubic  feet  of  free  air  per  minute 
required  to  operate  from  one  to  fifty  Rand  drills,  of  various 
sizes,  at  60  pounds  pressure  at  sea  level  and  run  under  average 
mining  conditions : 


TABLE   XLI. — Air  Required  to  Operate  Rand  Rock  Drills. 


Number  or  name. 


Kid. 


No.  I. 


Xo. 


No.  3. 


No.  3%.  \  No.  4. 


No. 


No.  7. 


Diam.  of  cylinder, 
in  inches. 


2i/ 


3/$ 


Jiff 


3X         3H 


4'A 


Number  of  drills. 


2  , 

3 

4 

5 

6 

7 
8 

9 
10 
12 

15 
20 

25 
30 
40 
50 


35 
61 
88 
"3 
135 
158 
185 
210 
231 
256 


53 
93 
133 
170 
204 
238 
280 
318 
350 
387 
460 

573 

756 

930 

1, 112 

1,482 

1,855 


64 
112 

160 
206 
246 
288 
340 
3S4 
423 
466 

554 

691 

914 

1, 120 

1.343 
1,790 
2,240 


95 
166 

238 
306 

365 
42S 
504 
580 
626 

693 
822 
1,030 
1,350 
1,665 
2,000 
2,660 
3,325 


103 

iSo 

258 

332 

396 

463 

545 

620 

680 

750 

890 

1, 112 

1,470 

1,800 

2,163 

2,880 

3,600 


112 

1 96 

280 

360 

430 

505 

593 

672 

740 

S17 

970 

1,210 

1,600 

1,960 

2,355 

3,140 

3,920 


132 
231 

330 
425 
50S 

595 
700 
792 
870 
964 
1, 140 

1.425 
1,880 
2,310 
2,780 
3,700 
4,620 


154 
270 

385 

495 

592 

693 

815 

924 

1,015 

1, 122 

1.330 

1,665 

2.200 

2,700 

3,240 

4,310 

5,400 


Following  is  an  appendix  to  above  table  giving  factor  for 
determining  free  air  per  minute  required  at  60,  70,  80,  90,  and 


436 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


lOO  pounds  pressure,  and  for  altitudes  from  sea  level  to  10,000 
feet  above : 


Factor 

OF  Multiplication. 

Atmospheric 
pressure, 

Altitude 

in  feet  above 

pounds 

Pressure  at  Drill. 

sea  level. 

per  square 
inch. 

60  pounds. 

70  pounds. 

80  pounds. 

90  pounds. 

100  pounds. 

14.7 

1. 00 

I-I33 

1.26 

1.40 

1-535 

500 

14-45 

1. 015 

I-I5 

28 

1.425 

1-563 

1,000 

14.12 

1.03 

1. 17 

31 

1-45 

1-59 

1.500 

13.92 

1.048 

1. 19 

33 

1.48 

1.62 

2,000 

13.61 

1.06 

I. 21 

35 

I-50 

1.645 

3,000 

13.10 

1. 10 

1-25 

40 

1-55 

1.70 

4,000 

12.61 

1. 131 

1.287 

443 

1.60 

1-755 

5,000 

12.15 

1. 17 

1-33 

495 

1.652 

1. 81 

6,000 

"•75 

1.20 

1-37 

537 

1.705 

1.87 

7,000 

11.27 

1.24 

1.42 

59 

1.76 

1-935 

8,000 

10.85 

1.282 

1.465 

645 

1.825 

2.00 

9,000 

10.45 

1.32 

I-51 

70 

I. go 

2.07 

10.000 

10.10 

1-365 

1-56 

755 

1.968 

2.143 

Example. — Take  the  case   of  three   2 14^ -inch    drills    at   60 
pounds,  at  sea  level.     This  requires  a  compressor  with  a  free 


Fig.  244.— the  slugger  rock  drill  valve  movement. 

air  capacity  of  133  cubic  feet.  Now  if  it  is  the  desire  to  oper- 
ate these  drills  at  80  pounds,  and  at  sea  level,  the  free  air  ca- 
pacity of  a  compressor  will  have  to  be  133  X  1.26  =  168  cubic 
feet  per  minute.  If  the  drills  are  to  work  at  an  altitude  of 
5,000  feet,  and  70  pounds  pressure  at  drill,  the  free  air  capacity 
required  will  have  to  be  133  X  1.33  =  177  cubic  feet  per  minute. 


THE   POWER   OF    COMPRESSED   AIR.  437 


IMPACT,     OR     THE     FORCE     OF     PERCUSSION,     IN     HAMMERS     AND 
PERCUSSION    DRILLS. 

The  force  of  a  blow  from  a  hammer  in  the  hand,  of  a  drop 
press,  a  pile  driver,  a  hammer,  a  rock  drill;  the  falling  of  solid 
bodies,  the  water  ram  in  pipes;  and  the  power  of  projectiles, 
produce  effects  deducible  from  the  general  laws  of  dynamics 
applicable  to  such  work. 

The  power  of  the  hand  hammer,  which  has  not  as  yet  been 
classed  among  the  "mechanical  powers,"  without  doubt  de- 
serves the  place  of  honor  as  the  most  ancient  and,  in  many 
respects,  the  most  wonderful  mechanical  power  known.  We 
daily  see  the  results  of  its  surprising  force,  effected  without  the 
complication  of  levers,  wheels,  or  wedges ;  and  apparently  hav- 
ing some  innate  power  superior  to  and  independent  of  the  prin- 
ciples of  mechanics  as  commonly  studied. 

In  order  to  enable  any  one  to  make  the  complete  compu- 
tation of  the  velocity  of  a  drop  hammer  in  the  drop  press,  a 
cushioned  air  hammer,  or  the  monkey  of  a  pile  driver,  when 
the  velocity  is  due  to  gravity  only,  the  power  of  impact  at  the 
moment  of  giving  the  blow  may  be  ascertained  from  the  known 
height  at  which  the  velocity  of  fall  commences.  The  effect 
due  to  cushioning  of  air  and  spring  hammers  will  be  an  accel- 
eration of  velocity  due  to  the  gross  pressure  at  starting,  and 
will  be  described  later  on. 

The  square  root  of  twice  gravity  (A/64.35)  multiplied  by  the 

square  root  of  the  height  (Vheight)  in  feet;  V2  ^  X  h,  or  8.02 

X  a/^  =  the  velocity  in  feet  per  second  at  the  instant  of  impact 

of  a  falling  body. 

Then  one-half  the  square  of  the  velocity  X  by  the  ^ — 

gravity 

—  X  — ,  or  more  simply  the  height  of  fall  X  by  the  weight,  gives 

the  number  of  foot-pounds  due  to  the  fall ;  and  the  distance  at 
which  the  force  of  the  blow  is  arrested  is  the  measure  of  the 


43^  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

force  of  percussion  or  impact.  It  is  as  much  more  than  the 
momentum  in  foot  pounds  as  the  distance  of  arrest  bears  to  a 
foot.  Thus,  if  at  half  a  foot  the  impact  is  twice  the  foot 
pounds,  at  i  inch  it  is  12  times,  and  so  on  through  the  frac- 
tions of  an  inch ;  at  i/(  inch  it  is  48  times,  and  at  ^^  inch 
it  is  384  times.  This  latter  arrest  represents  the  impact  of 
hardened  surfaces,  where  the  elasticity  of  the  metals  largely 
represents  the  small  movement  at  impact,  and  of  which  the  re- 
bound of  a  hammer  from  the  face  of  a  hardened  anvil  repre- 
sents the  reactive  effect  of  the  foot  pounds  due  to  the  momen- 
tum of  the  fall. 

A  small  hammer  swiftly  wielded  will  accomplish  that  which 
would  otherwise  require  a  direct  pressure  of  several  tons. 
Seeking  the  cause  of  its  mystic  power,  the  principles  of  accu- 
mulated work  or  energy  stored  in  weight  and  velocity  will  ac- 
count for  the  varied  effects  we  obtain. 

In  striking  a  blow  with  a  hammer  upon  the  head  of  a  chisel 
there  are  two  forces  brought  into  action,  viz.,  the  force  of  grav- 
ity and  muscular  force  to  increase  the  velocity,  so  that,  at  the 
instant  of  striking,  the  hammer  may  have  a  velocity  of  from  20 
to  50  feet  per  second ;  the  effect  at  this  moment  is  the  same  as 
if  the  final  velocity  had  existed  throughout  the  whole  of  the 
stroke.  Assuming  32  feet  per  second  as  the  actual  velocity  at 
moment  of  impact,  then  the  force  will  be  the  same  as  if  the 
hammer  had  fallen  from  a  height  of  the  square  of  the  velocity, 

divided  by  twice  gravity,     —  )  or  -^ —  =   16  feet. 

\2^J  64.33 

With  a  hammer  weighing  2  pounds,  then,  the  accumulated 
work  or  energy  will  be  16  X  2  =  32  foot  pounds. 

Supposing  that  the  face  of  the  hammer  moves  one-eighth  of 

an  inch  after  touching  the  head  of  the  chisel  before  the  energy 

is  all  absorbed,  then  the  result  will  approximately  be  the  same 

1 2 
as  a  direct  pressure  or  dead  load  of  32  x  -^  =^  3)072  pounds, 

"8 

or  upward  of  i^  net  tons;  but  this  is  only  partially  true. 


THE    POWER   OF   COMPRESSED    AIR.  439 

More  correctly  it  would  be  an  average  pressure  of  3,072 
pounds,  being  considerably  more  at  the  commencement  of  con- 
tact with  the  chisel  and  reduced  at  the  end  of  the  chisel  cut  to 
the  mere  weight  of  the  hammer  and  chisel. 

The  hammer  may  be  a  self-adjusting  mechanical  power ;  for 
if  the  material  be  harder,  so  as  to  give  more  resistance  to  the 
chisel,  the  cut  will  not  be  so  great,  and  therefore  the  force  of 
percussion  will  be  greater.  For  instance,  if  the  movement  of 
the  chisel,  as  above  stated,  had  been  only  one-sixteenth  of  an 
inch,  the  force  would  have  been  doubled  or  equal  to  a  pressure 
of  3  tons  instead  of  i-|-  tons. 

But  there  is  a  limit  to  the  effect ;  otherwise  the  blow  would 
be  measured  by  thousands  of  tons,  until  the  rigidity  of  the  mass 
receiving  the  blow  was  balanced  by  the  elasticity  of  the  mate- 
rial giving  and  receiving  the  blow.  This  is  beautifully  illus- 
trated when  striking  the  hardened  face  of  an  anvil  with  a  ham- 
mer, where  nearly  the  whole  force  of  the  blow  is  returned  in 
the  rebound  of  the  hammer. 

The  intensity  or  quality  of  a  hammer  blow  is  of  great  im- 
portance in  the  various  materials  upon  which  it  is  used ;  the 
man  of  iron  and  steel  using  a  quick  blow,  while  the  man  of 
stone  uses  a  slower  blow  with  a  heavier  hammer,  or  the  elastic 
mallet,  which  gives  a  pushing  blow — each  method  being  the 
best  in  its  way,  because  suited  to  the  material  operated  upon. 

When  we  reach  the  domain  of  "power  behind  the  throne," 
and  have  steam  and  compressed  air  to  aid  the  force  of  a  blow, 
the  elastic  force  behind  the  hammer  gives  it  the  velocity  due  to 
impractical  height  of  fall  in  large  bodies,  and  thus  adds  power 
to  a  short  stroke,  and  enables  that  control  over  the  movements 
of  a  great  steam  or  air  hammer  so  necessary  for  the  successful 
working  of  the  immense  forgings  now  being  made.  The  later 
improvements  in  hydraulic  forge  hammers  have  enabled  the 
enormous  hammer  pressure  of  4,000  tons  to  be  utilized  in 
making  the  forgings  for  modern  ordnance. 

In  computing  the  power  of  direct-acting  steam  or  air-driven 


440  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

forge  hammers,  we  have  the  elements  of  the  initial  pressure, 
from  which  must  be  deduced  the  m.ean  pressure  throughout  the 
stroke,  the  weight  of  the  hammer,  rod,  and  piston,  and  the 
length  of  stroke,  from  which  to  obtain  the  positive  work  of  the 
hammer  per  stroke ;  against  which  are  the  back  pressure  from 
a  cushioned  blow,  or  the  constant  retarding  pressure  from  the 
exhaust  with  a  free  stroke,  together  with  the  friction  of  the 
moving,  parts,  which  constitute  the  sum  of  the  deductions  to  be 
made  from  the  computed  positive  impact  of  the  hammer. 

For  the  purpose  of  arriving  at  the  approximate  power  of 
percussion  of  a  steam  or  air  hammer,  we  may  assume  for  the 
conditions  of  computation  a  weight  of  4,000  pounds  for  the  pis- 
ton, rod,  and  hammer,  with  a  diameter  of  cylinder  of  20  inches 
and  a  maximum  stroke  of  3  feet,  with  air  or  boiler  pressure  at 
100  pounds. 

From  the  nature  of  the  work  of  an  air  or  steam  hammer, 
both  the  pressure  and  stroke  must  be  extremely  variable  below 
the  limit  of  greatest  capacity,  so  that  for  the  maximum  effect 
we  have: 

W  =  Weight  of  hammer,  piston,  and  rod  =  4,000  pounds. 

S  =  Greatest  stroke  of  piston  ==  3  feet. 

P  =  Pressure,  area  of  piston  314  square  inches  x  50  pounds 
assumed  mean  pressure  =  15,700  pounds. 

g  =  Gravity,  or  the  velocity  of  a  falling  body  at  the  end  of 
one  second  of  time  =  32. 16. 

///  =  Mass  =  Weight  divided  by  gravity  —  ~ — -  =  124.378. 

/  =  Total  accelerating  force  P  -f  W  =  19,700  pounds. 

a  =  Acceleration  =  •'-^  = ' =  158.388. 

in  in 

V  =  Velocity  of  impact  = 

, P-hW  o       ^     ^  A 

^2  rt  S  =  -^  S  — =  30-827  feet  per  second. 

Ill 

E  =  Energy  = 

^  ^  /P  +  W\ 

in  2  vS  1 ■ I 

^_l!  =  ^- 1  =  S  P  +  S  W  =  59, 100  foot-pounds. 


THE    POWER    OF    COMPRESSED    AIR.  441 

If  the  energy  of  the  blow  is  arrested  by  the  compression  of 
the  forging-  and  the  spring  of  anvil  in  a  distance  of  one  inch 
from  the  point  of  contact,  the  measure  of  the  force  of  percus- 
sion must  be  multiplied  by  the  distance  of  arrest  in  fractions  of 
a  foot  for  its  true  value.  Thus  for  one  inch  12  X  59,100  = 
709,200  pounds,  or  over  354  tons  =  the  static  pressure  due  to 
percussion. 

In  striking  a  cold  mass  of  iron  upon  the  anvil  block  with  a 
yield  of  only  one-quarter  of  an  inch  the  enormous  pressure  of 
over  1,400  tons  would  be  attained. 

From  the  total  accelerating  force,  the  friction  of  piston,  rod, 
and  slides  should  be  deducted;  amounting  in  well-constructed, 
direct-acting  hammers  to  from  3  to  5  per  cent.  The  resistance 
to  the  power  of  a  full  hammer  blow  from  the  back  pressure  of 
the  exhaust  is  of  some  importance,  and  may  possibly  amount  to 
from  3  to  5  pounds  per  square  inch,  or  about  10  per  cent  on  the 
total  effect,  as  above  stated. 

The  effect  of  cushioning  of  the  piston  is  a  beautiful  illustra- 
tion of  the  control  that  can  be  made  over  an  intense  mechanical 
force,  that  by  the  mere  movement  of  a  hand  may  have  its 
power  varied  from  o  to  a  percussion  pressure  of  over  1,300  tons. 

The  action  of  a  rock  drill  is  somewhat  unique  in  its  persist- 
ence in  overcoming  the  resistance  of  the  various  kinds  of  rock 
to  its  efforts  to  penetrate  their  depths.  It  does  its  work  not  so 
much  by  the  high  percussion  pressure  of  a  single  blow,  but 
rather  by  the  quick  repetition  of  blows  just  suited  for  effective 
work  and  for  accomplishing  a  given  depth  of  hole  in  the  shortest 
possible  time.  Its  peculiar  valve  gear  and  short  stroke  make 
its  percussive  force  almost  wholly  due  to  pressure  on  the  pis- 
ton, which  is  made  thoroughly  controllable  at  the  hand  valve 
and  feed  screw.  By  this  means  the  drill  may  be  run  at  a 
stroke  and  pressure  that  gives  the  fastest  cutting  power;  and 
as  this  may  not  be  its  longest  stroke,  which  cushions  the  blow 
and  reduces  the  number  of  blows  per  minute,  a  medium  of  from 
75  to  85  per  cent,  of  the  full  stroke  is  found  to  be  most  effective. 


442  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

The  friction  of  the  drill  steel  in  the  hole,  added  to  the  fric- 
tion of  the  piston  rod,  piston,  and  rotating  device  or  rifle  bar, 
is  a  serious  drawback  to  the  otherwise  large  theoretical  power 
of  percussive  pressure  in  the  rock  drill. 

Take,  as  an  example,  the  theoretical  percussive  blow  from 
a  medium  size  rock  drill  of  say  3  inches  diameter  of  piston, 
running  at  60  pounds  pressure  with  5 -inch  stroke,  having  an 
effective  piston  area,  after  deducting  the  area  of  the  rifle  bar, 
of  6  square  inches;   weight  of  piston  and  drill  steel,  50  pounds. 

The  friction  of  the  pipe  and  passages,  throttling  by  the 
valve  and  back  pressure  from  the  exhaust,  together  with  the 
following  of  the  steam  or  air  pressure  for  three-quarters  of  the 
stroke,  will  reduce  the  mean  pressure  to  40  pounds. 

Then  by  the  formulas  as  given  for  the  steam  or  air  hammer, 
the  energy  of  the  blow  will  be  the  total  mean  pressure  on  the 
piston  multiplied  by  the  stroke  in  fraction  of  a  foot,  plus  the 
stroke  multiplied  by  the  weight,  or  6  square  inches  X  40  pounds 
X  -Y2  +  fV  ^   5°  pounds  =   120.83  foot-pounds. 

Then  if  the  drill  penetrate  the  rock  i  of  an  inch  at  each 

1 2 
stroke  the  theoretical  effect  of  percussion  will  be  __  or  96  X 

120.83  =   1 1,699  pounds,  or  nearly  6  tons  static  pressure. 

A  large  allowance  from  the  theoretical  effect  must  be  made 
for  the  actual  effect,  by  the  assumed  value  of  the  friction  of  the 
drill  steel  on  the  sides  of  the  hole,  and  other  moving  parts,  as 
well  as  for  the  resisting  effect  of  water  and  debris  of  drilling, 
which  always  more  or  less  clog  the  drill  hole. 

The  average  running  time  of  drills  on  open  rock  work  is 
about  five  hours  per  day,  and  the  average  of  250  strokes  per 
minute  or  75,000  strokes  per  day  is  probably  a  fair  average 
day's  work.  This  at  -|-inch  depth  of  cut  and  10  strokes  to  make 
a  circuit  of  revolution  of  the  steel  to  complete  the  cut  will  rep- 
resent ^^'^'^^  =  —  —  78  feet  lineal  depth  of  holes  for  a  day's 
96  10 

work  in  rock  of  medium  hardness — limestone.     In  granite  from 


THE    POWER   OF    COMPRESSED    AIR.  443 

50  to  60  feet  is  about  an  average  day's  work,  owing  to  the  less 
penetration  of  the  drill  per  stroke ;  while  in  marble,  with  dry- 
short  holes,  a  very  much  larger  depth  of  holes,  200  to  250  feet, 
has  been  drilled.  In  this  kind  of  work  the  actual  running  time 
of  the  drill  is  increased  by  the  increased  facilities  of  adjustment 
from  hole  to  hole  and  the  use  of  only  a  single  drill  steel. 

The  principles  governing  the  force  of  a  blow  may  be  ap- 
plied to  the  air  hammer  as  used  for  chipping  or  riveting.  The 
entire  elimination  of  slides  and  drill  friction  in  the  air  hammer 
leaves  only  the  friction  of  the  piston  to  be  considered,  and  this 
is  so  small  that  5  per  cent  of  its  percussive  power  is  ample  to  be 
deducted  from  its  total  computed  static  pressure.  A  li-inch 
hammer  piston,  weighing  2  pounds,  with  4-inch  stroke,  running 
with  60  pounds  air  pressure,  will  have  1.76  square  inches  X  60 
X  -g-  foot  =  35  -[-  2  X  -g-  =  35.66  foot-pounds  per  blow,  less  5 
per  cent  =33.8  foot-pounds.  If  the  chisel  moves  forward  ^ 
inch  at  each  blow,  then  33.8  X  16  X  12  =  6,489  pounds  is  the 
static  weight  equivalent  to  each  blow.     Then  if  the  hammer 

makes   500  blows  per  minute,  - —    =  31   inches  would  be  the 

length  of  chip  cut  per  minute ;  and  so  on  for  any  work  of  per- 
cussion by  air  hammers. 


Chapter  XXIII. 


PNEUMATIC  TOOLS. 

THE  PNEUMATIC  HAMMER 

AND  ITS  WORK 


PNEUMATIC   TOOLS. 

THE    PNEUMATIC    HAMMER    AND    ITS    WORK. 

The  engineering  industry  at  the  present  time  is  enjoying 
a  period  of  activity  quite  unprecedented  in  its  history,  and,  as 
a  consequence,  is  calling  for  an  immense  increase  in  the  num- 
ber of  its  labor-reducing  machines.  Prominent  among  these 
are  portable  pneumatic  tools  and  appliances,  and  it  is  not  too 
much  to  say  that  there  is  every  indication  of  their  extended 
application.  They  have  been  used  for  a  considerable  time,  al- 
though, with  certain  exceptions,  they  have  not  been  well  ap- 
preciated until  the  last  few  years,  and  considering  their  impor- 
tance and  the  valuable  assistance  they  are  rendering  to  the 
shipbuilding  and  man)'  other  industries,  it  is  somewhat  singular 
that  comparatively  little  information  has  been  circulated  about 
them  except  by  trade  descriptions.  Doubtless  some  explana- 
tion for  this  is  to  be  found  in  the  fact  that  their  practical  appli- 
cation is  of  comparatively  recent  date,  and  further,  that  some 
of  the  earlier  tools  were  unsatisfactory.  Whatever  the  cause 
may  be,  it  appeared  that  the  subject  was  one  which  would  be 
of  vital  interest  in  its  relief  to  the  weary  muscle  of  the  me- 
chanic. The  author,  at  the  same  time,  is  aware  that  the  sub- 
ject is  by  no  means  a  new  one  to  some  of  the  leading  and  more 
enterprising  firms,  who  have  experimented  with  pneumatic 
tools  for  some  years  past ;  and  he  also  recognizes  that  certain 
kinds  of  portable  pneumatic  riveters  and  other  appliances  have 
been  in  constant  use  for  a  considerable  time,  but  he  ventures 
to  hope  that  the  various  tools  described  and  illustrated  in  this 
work  may  be  of  interest,  as  showing  what  has  been  achieved 
up  to  the  present  date.     The  various  tools  which  can  be  driven 


448  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

by  compressed  air  are  many,  and  are  rapidly  increasing  in 
number. 

Since  the  mechanism  employed  for  utilizing  compressed  air 
to  secure  a  percussive  action  is  essentially  the  same  in  both 
hammers  and  riveters,  it  will  be  sufficient  to  describe  the  mech- 
anism in  the  different  kinds,  and  for  this  purpose  the  hammer 
will  first  serve. 

Hammers  may  broadly  be  divided  into  two  types,  viz.,  the 
valveless  hammer  and  the  valve  hammer.  This  is  a  convenient 
description,  yet  perhaps  not  strictly  correct,  because  although 
the  valveless  hammer  has  no  valve  beyond  the  striking  piston, 
this  is  itself  a  valve  to  effect  the  proper  admission  of  air  to 
alternate  ends  of  the  working  cylinder;  while  in  the  valve  ham- 
mer a  reciprocating  valve,  working  either  at  right  angles  to  or 
parallel  with  the  striking  piston,  acts  in  combination  with  it  to 
regulate  the  inlet  and  exhaust  of  the  compressed  air. 

Valveless  hammers  have  essentially  a  short  stroke,  and,  al- 
though economical  in  air  consumption  in  relation  to  the  number 
of  blows  given,  they  will  not  compare  with  valve  hammers  in 
giving  powerful  blows  which  are  necessary  in  heavy  chipping 
or  riveting.  Owing,  however,  to  their  simple  construction, 
they  have  probably  a  longer  life  than  the  valve  hammers,  and 
for  such  purposes  as  beading  flues,  light  calking  and  chipping, 
and  especially  carving  in  stone,  etc.,  they  compare  very  favor- 
ably with  valve  hammers.  The  speed  of  the  valveless  hammers 
is  very  high,  being  i,ooo  to  2,000  strokes  per  minute. 

Valve  hammers  will  probably  secure  the  market  for  general 
and  heavy  chipping,  calking,  and  riveting.  Their  speed  for 
ordinary  work  ranges  from  1,500  to  2,000  blows  per  minute, 
although  they  can  be  driven  much  faster.  Their  stroke,  how- 
ever, is  considerably  longer  than  that  of  the  valveless  hammers 
and  the  blow  struck  correspondingly  greater.  There  is  more 
air  lost  in  the  ports,  but  other  advantages,  including  better  con- 
trol for  using  the  air  expansively,  overcome  this  small  defect. 
It  is  well  known  that  the  nature  of  a  blow — whether  lisfht  or 


PNEUMATIC   TOOLS. 


449 


heavy — on  various  materials,  produces  an  effect  apart  from  tlie 
actual  work  done  as  measured  in  foot-pounds.  For  example, 
10,000  small  blows  representing  a  certain  number  of  foot- 
pounds might  fail  to  produce  a  desired  result,  which  a  smaller 
number  of  heavy  blows,  representing  less  energy  in  foot- 
pounds, would  effect.  Having  now  considered  the  claims  and 
advantages  of  the  different  types  of  hammers,  all  of  which  it 
may  be  stated  can  be  worked  economically  at  from  60  pounds 
to  80  pounds  per  square  inch,  reference  must  be  made  to  the 
illustrations  in  order  to  explain  their  construction  and  action 
under  compressed  air. 

Fig.  245  shows  in  section  a  "  Ross  "  hammer  in  which  the 
striking  piston  becomes  the  valve  to  control  the  admission  and 


-^ 


Fig.  245.— ROSS  pneumatic  hammer. 


exhaust  of  the  working  fluid.  A  represents  the  outer  casing, 
made  from  solid  drawn  steel  tube,  bored  and  fitted  w'ith  a  phos- 
phor-bronze liner,  B,  which  forms  the  cylinder  in  which  the 
piston  works ;  E  the  striking  piston  made  from  a  steel  forging, 
ground  to  fit  the  cylinder;  D,  the  exhaust  ports,  open  to  the 
atmosphere  through  the  valve  G,  C  and  C  the  admission  ports, 
admitting  compressed  air  to  alternate  ends  of  the  piston ;  K, 
another  port  always  open  to  the  air  supply ;  G,  the  exhaust 
valve;  H,  the  trigger  actuating  the  same;  F,  the  phosphor- 
bronze  handle,  to  which  compressed  air  is  admitted  at  the  point 
F' ;  L,  a  piston  cushion,  has  always  full  and  constant  pressure 
behind  it  from  the  air  supply  through  the  port  F ;  and  M 
shows  the  working  tool. 

It  must  be  noted  that  this  hammer  is  caused  to  work  by  the 
29 


450  COMPRESSED    AIR   AND    ITS   APPIICATIONS. 

opening  of  the  exhaust  and  not  by  regulation  of  the  admission. 
The  direction  taken  by  the  air  under  pressure  when  connected 
to  the  handle  at  F'  will  be  readily  seen  by  noting  the  arrows. 
The  piston  is  slightly  reduced  in  diameter  in  the  middle,  and 
the  inside  edges  of  the  two  collars  thus  produced  form  the  cut- 
off edges  for  pressure,  while  their  outsides  govern  the  exhaust 
ports.  It  will  be  seen  that  when  the  piston  is  in  the  middle  of 
its  stroke  there  is  a  dead  point,  the  compressed  air  finding  admis- 
sion only  to  the  chamber  formed  by  the  reduced  portion  of  the 
piston,  since  the  ports  C  and  C  are  all  cut  off  from  admission 
of  compressed  air,  but  this  does  not  interfere  with  its  proper 
working,  as  the  port  cover  is  very  small.  Moreover,  when 
starting,  the  piston  will  fall  either  to  one  end  of  the  cylinder  or 
the  other  by  gravity,  and  when  at  work  the  momentum  carries 
it  over  the  dead  point.  The  cut  shows  the  front  exhaust  valve 
open,  and  the  piston  just  commencing  to  make  its  forward 
stroke.  Air  flows  through  A',  thence  through  the  port  C,  pass- 
ing between  the  annular  space  formed  between  the  liner  and 
the  outer  casing,  and  back  through  C  to  back  of  piston,  thus 
driving  it  forward.  At  the  same  time,  exhaust  takes  place 
through  D.  The  same  action  takes  place  on  the  backward 
stroke,  when  the  forward  ports,  6^  and  C\  are  then  in  commu- 
nication with  A'.  In  order,  as  far  as  possible,  to  eliminate 
vibration,  a  condition  which  is  present  in  all  hammers,  the 
cushion  piston.  A,  has  been  introduced  at  the  rear  of  piston. 

Fig.  246  shows  in  section  a  "  Q  and  C  "  single  hammer.  A 
represents  a  bronze  handle,  in  which  is  fitted  the  steel  liner,  B, 
which  forms  the  working  cylinder;  C,  the  striking  piston, 
which  acts  as  its  own  valve ;  D,  the  outer  cap,  connecting  the 
liner  to  the  handle;  E,  the  throttle  valve;  F,  the  trigger  actu- 
ating the  same ;  and  G,  the  point  to  which  the  air  supply  is 
attached.  The  action  of  the  hammer,  on  the  trigger  being  de- 
pressed, is  as  follows: 

The  air  having  passed  the  valve,  E,  flows  along  the  passage, 
d,  and  through  a  large  air  port  into  the  cylinder  or  pressure 


PNEUMATIC    TOOLS. 


451 


Fig.  246.— q  and  c  hammer. 


chamber;  this  has  the  effect  of  maintaining  a  constant  pressure 
Under  the  shoulder  of  the  piston  and  tends  to  drive  it  back- 
ward. When,  however,  the  ports  b,  in  the  piston  C,  which 
are  also  large  openings,  come 
into  communication  with  the 
cylinder,  the  pressure  fills  the 
hollow  portion  of  the  piston 
and  the  cylinder  in  its  rear, 
driving  the  piston  forward  to 
strike  its  blow.  At  this  in- 
stant the  piston  ports  come 
into  communication  with  the 
exhaust  port  r,  when  the  press- 
ure under  the  piston  shoulder  again  returns  the  piston,  and 
the  blows  are  repeated  in  rapid  succession — as  many  as  1,000 
to  2,000  per  minute.  It  will  be  noticed  that  in  this  arrange- 
ment of  ports  the  air  is  used  expansively.  The  same  type  of 
hammer  is  made  in  a  modified  form,  being  provided  with  a 
second  piston  placed  in  the  rear  of  the  other,  the  actuating 
fluid  working  between  the  two  pistons  for  the  forward  stroke. 
It  is  claimed  for  this  that  vibration  is  reduced  to  a  minimum. 

Fig.  247  shows  a  hammer  constructed  on  similar  lines  as 
the  "  Q  and  C  "  with  the  addition  of  a  counterbalance  piston, 

which  by  its  reaction  and 
cushion  relieves  the  body  of 
the  hammer  and  the  hand 
from  excessive  jar. 

In     the    duplex    riveter 
(Fig.  248)  the  striking  pis- 

FlG.r47.-COUXTERB.^LANCKD  H.AMMER.  ^^^^    ^^    -^    CUCaSed   iu    a    Strik- 

ing cylinder,  C,  so  that  the  tool,  T.,  receives  a  blow  alternately 
from  the  hammer  piston.  A,  and  from  the  cylinder,  C  on  the 
tool  socket,  H.  The  method  of  operation  is  shown  by  the 
differential  piston  areas.  By  the  alternating  motion  and  stroke 
of  the  two  pistons  the  hand  is  relieved  from  jar. 


452 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  248.— the  duplex  riveter. 


Coming-  now  to  the  valve  hammers,  to  describe  them  briefly 
and  the  same  time  accurately  is  not  an  easy  matter,  because 
although  they  are  simple  in  action  and  not  excessively  com_pli- 

cated  with  regard  to  the 
number  of  working  parts,  yet 
their  movements  and  arrange- 
ments of  ports  are  such  as  to 
make  their  description  some- 
what difficult. 

The  "Little  Giant"  Hammer. — This  is  illustrated  in 
Figs.  249  and  250,  to  which  the  following  reference  applies:  A, 
working  cylinder ;  B,  piston  hammer ;  D,  working  tool ;  £,  con- 
trolling valve;  £',  steel  seating  for  vSame;  F,  handle;  G  G\ 
throttle  valve  bushing;  H,  throttle  valve;  /,  trigger  actuating 
same;  a,  bore  of  cylinder;  a-,  passage  leading  from  cylinder  to 
top  of  valve  chamber;  tf,  passage  from  front  end  of  cylinder  to 
annular  space  in  valve  chamber;  a\  exhaust  passage  at  rear  end 
of  cylinder  leading  to  exhaust  through  interior  of  valve ;  «', 
bye-pass  from  a" ;  a,  exhaust  passage  in  forward  end  of  cylinder 
to  atmosphere ;  b,  reduced  portion  of  striking  piston  ;  b\  annular 
chamber  formed  by  such  portion  ;  c,  opening  into  the  control- 
ling valve  bushing;    c\  opening  into  cylinder  from  valve  bush- 


FlG.   249  -  LITTLE  GIANT   HAMMER. 

ing;  ^^  annular  portion  in  valve  bushing;  c\  openings  in  valve 
E,  leading  to  exhaust  port,  r";  c\  central  chamber  of  valve;  r", 
exhaust  to  air  in  handle ;  c\  enlarged  diameter  of  valve  for 
cushioning;  e\  recess  behind  /;  c'\  small  boss  on  top  of  valve. 
Fig.  249  represents  a  longitudinal  sectional  elevation  of  a  ham- 


PXEL  MATIC    TOOLS. 


453 


mer  with  the  striking  piston  at  the  rear  end.  Fig.  250  is  a 
similar  view,  but  of  the  opposite  half,  and  showing  the  striking 
piston  at  the  forward  end  of  stroke.  Figs.  251  and  252  show 
the  handle  and  valve  portion  in  section  with  the  valve  at  the 
top  and  bottom  positions  respectively. 

The  action  of  the  tool  is  as  follows:  air  under  pressure 
having  been  admitted  by  operating  the  valve  //,  passes  through 
the  opening  e,  and  under  the  head  of  the  valve  E,  thus  forcing 
it  in  the  position  shown  in  Fig.  251.  The  air  is  then  able  to 
pass  into  the  cylinder  through  the  opening  c\  and  thus  forces 
the  piston  forward  into  the  position  shown  in  Fig.  250.     It  will 


Fig.  250.— little  giant. 
Piston  down. 


be  noted  that  the  piston  is  reduced  in  diameter  at  /',  which  to- 
gether with  the  c\'linder  forms  a  chamber,  //,  so  that  as  the 
piston  nears  its  forward  limit  of  stroke,  air  pres.sure  enters  the 
chamber  //,  from  the  passage  a\  which  is  in  direct  communi- 
cation with  space  c.  At  the  same  time  the  passage  a"  is 
brought  into  communication  with  b\  and  thus  the  air  passes 
along  to  the  top  of  the  valve  E,  and  forces  it  into  the  bottom 
position,  as  shown  in  Fig.  252.  When  the  valve  is  in  this  posi- 
tion a  clear  way  for  the  compressed  air  is  open  to  the  front  end 
of  piston  through  r,  e\  and  a\  thus  effecting  the  return  of  the 
piston.  Thus  far  the  live  air  admission  has  been  dealt  wilh  to 
drive  both  piston  and  valve  in  both  directions.  Coming  now 
to  the  exhaust  and  taking  the  piston  in  its  rearward  motion 
first,  the  air  escapes  along  the  passage  a\  and  through  the 
openings,  c\  in  valve  and  out  through  c\     In  its  forward  mo- 


454 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


tion  the  piston  exhausts  first  through  a\  which  leads  direct  to 
outer  atmosphere.  When  a'  is  passed,  the  air  escapes  through 
(f,  which  is  open  to  atmosphere  through  i^,  e\  and  c\  when  the 
valve  E  is  up.  The  exhaust  of  the  valve  is  effected  thus: 
During  the  backward  movement  of  the  piston,  and  as  its  annu- 
lar portion  is  passing  a",  it  permits  the  air  pressure  on  top  of 
valve  E  to  escape  through  a",  a"",  into  b\  a\  and  a\  to  atmos- 
phere, with  the  result  that  superior  pressure  under  valve  head 
from  e  again  lifts  the  valve.  The  valve  is  forced  into  its  bot- 
tom position  due  to  its  area  on  the  top  being  larger  than  the 


Fig.  251.— little  giant. 
Ready  to  strike. 


Fig.  252. -little  giant. 
Return  stroke. 


ring  underneath  its  head.  It  is  obvious  that  both  the  striking 
piston  in  its  backward  stroke  and  the  valve  in  both  directions 
should  receive  some  form  of  cushioning,  so  as  to  reduce  shock 
and  prevent  injury  to  valve  and  cylinder.  In  the  piston  this 
is  effected  by  its  closing  the  port  a\  before  the  end  of  its  stroke. 
In  the  valve  the  desired  cushioning  is  secured  in  its  upward 
stroke  by  means  of  the  boss  r'",  which  causes  the  air  to  escape 
rather  slowly  into  a".  In  its  downward  stroke  the  cushioning 
is  effected  thus :  The  portion  e^  of  the  valve  E  is  of  diameter 
nearly  equal  to  the  small  bore  of  the  valve  bushing,  and  there 
is  also  provided  a  small  groove,  i-\  Fig.  251.  When  the  valve 
is  moving  down,  the  portion  r  first  enters  the  small  bore  of 
the  valve  chamber,  and  this  tends  to  retard  the  passage  of  the 


PNEUMATIC    TOOLS.  455 

air  through  the  bore,  and  permits  the  excess  of  air  to  act  as  a 
cushion.  Up  to  a  certain  limit  the  same  hammer  may  be  used 
to  give  light  or  heavy  blows,  and  this  may  be  effected  by  regu- 
lating the  amount  of  opening  given  to  the  throttle  valve.  It  is 
not  desirable,  however,  simply  to  rely  upon  the  trigger  to  do 
this,  but  preferably  to  provide  a  regulator,  so  that  however 
hard  the  trigger  may  be  pushed  it  only  opens  the  valve  the  de- 
sired amount.  In  the  "  Little  Giant  "  hammer  this  result  is 
obtained  by  making  the  throttle  valve  bushing  in  two  portions, 
G  and  G  '.  The  part  G  is  fixed  to  the  handle,  while  G  '  is  capable 
of  being  screwed  in  or  out.  The  effect  of  this  adjustment, 
when  taken  in  combination  with  the  valve  H  and  the  trigger 
/,  is  such  that  when  G^  is  unscrewed,  the  port  g'  may  be 
moved  into  such  a  position  that  the  valve  H  can  be  pushed  by 
the  trigger  /  to  the  limit  of  its  stroke  without  uncovering  the 
port  g'  at  all,  and  by  adjustment  of  the  part  G" '  any  desired 
opening  may  be  given  for  the  admission  of  air.  In  order  to 
put  the  valve  H  in  equilibrium  a  small  opening  admits  the 
compressed  air  to  either  side  of  it,  which,  together  with  the 
spring  shown,  effects  the  desired  result.  It  will  be  obvious 
that  fewness  of  parts,  and  especially  of  joints,  are  desirable  in 
the  construction  of  a  tool  using  compressed  air  at  high  press- 
ure, since  the  possibility  of  leakage  is  thereby  considerably 
reduced.  Another  feature  of  this  hammer  is  the  economical 
use  of  the  compressed  air,  due  to  the  cushioning  of  the  moving 
parts  taking  place  on  the  exhaust  air  rather  than  from  the  ad- 
mission of  live  air,  and  taking  this  in  connection  with  the  solid 
con.struction  of  the  valve,  the  same  being  well  cushioned  in 
both  directions  of  its  travel,  the  "Little  Giant"  type  is  likely 
to  prove  both  an  economical  and  a  good  wearing  hammer. 

The  "Boyer"  Hammer. — Figs.  253  and  254  show  sectional 
views  of  a  Boyer  hammer,  in  which  the  following  letters  of 
reference  indicate  the  various  parts  referred  to:  A,  the  work- 
ing cylinder;  D,  the  handle;  G,  the  air  passage  from  throttle 
valve    to    cylinder;     G\  throttle   valve;    //,   trigger   actuating 


456 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


same;  /,  the  valve  block;  /',  cap  at  end  of  same;  A',  the  work- 
ing tool;  M,  the  piston,  consisting  of  a  solid  piece  of  turned 
steel  fitting  the  bore  of  the  cylinder  and  provided  with  a  recess, 
M'\  O,  the  valve;  P,  passage  from  cylinder  to  small  space  e\ 
Q,  passage  from  cylinder  to  small  space  n ;  R,  passage  from 
front  end  of  cylinder  to  small  space  m;  S,  port  leading  from 
space  e  to  front  of  cylinder  through  passage  R;  T,  passage 
from  cylinder  through  ^  to  spacer-;  T\  from  air  supply  to 
cylinder ;  X,  from  air  supply  to  e. 

X  is  only  necessary  to  supply  air  to  front  end  of  piston  via 
5  and  R  and  to  hold  the  valve  in  rear  position.     Other  letters 


Fig.   253  -  THE   BOVER. 

ston  down. 

on  the  drawings  are  referred  to  in  the  following  description  of 
the  working  of  the  hammer: 

Fig.  253  represents  the  piston  in  its  forward  and  the  disc 
valve  in  its  rearward  position.  The  compressed  air  having  been 
admitted,  passes  along  the  passage  G,  and  then  into  space  e\ 
and  acts  on  small  area,  d,  of  the  disc  valve  O,  and  tends  to 
force  the  valve  forward,  but  air  pressure  in  space  e,  admitted 
by  the  passage  X,  acting  upon  the  large  area  of  the  valve,  will 
hold  the  valve  in  the  rearward  position  against  the  pressure 
acting  on  the  small  area.  The  air  will  pass  from  space  f, 
through  passages  S  and  R,  to  the  front  end  of  the  piston,  driv- 
ing the  latter  backward,  the  rear  end  of  the  cylinder  being  open 
to  exhaust  through  the  slots  in  valve  O  and  groove  //,  the  lat- 
ter being  constantly  open  to  the  atmosphere  through  passages 


PNEUMATIC    TOOLS, 


457 


Fig.  254.— the  bover. 
Piston  up. 


/,  k.  As  the  piston  moves  backward,  it  uncovers  ports  P  and 
Q,  and  the  pressure  in  front  end  of  cylinder  will  exhaust 
through  the  groove  and  passages,  j\  k,  to  the  atmosphere ;  the 
front  end  of  the  passage  P  will  be  uncovered  by  the  front  end 
of  the  piston  at  the  same  time  as  the  front  end  of  the  passage 
Q,  and  the  air  in  space  c  will  escape  through  passages  P  Q, 
groove  ;/,  and  passages  o,  t,  j,  k,  to  the  outer  air.  Passage  P 
being  larger  than  passage  A',  by  which  the  air  is  supplied  to 
the  space  e,  the  pressure  on  the  large  area,  c,  of  the  valve  O 
will  be  greatly  diminished,  so  that  the  pressure  acting  on  the 
small  area,  d,  of  the  valve  O  will  force  the  valve  forward  to 
the  position  of  Fig,  253, 
whereupon  the  ring  of  the 
valve  O  will  close  the  pas- 
sage X,  and  cut  off  the  sup- 
ply of  air  to  space  e,  there- 
by permitting  pressure  to 
hold  the  valve  in  the  forward 
position.  As  the  piston  moves  forward  and  finally  strikes  a 
blow  on  the  chisel,  the  air  in  front  can  escape  through  passage 
Q  until  the  latter  is  closed  by  the  front  end  of  the  piston,  and 
thereafter  can  escape  through  passage  R,  grooves  vi,  a,  and  ;/, 
and  passages  c^  i,j,  and  k,  to  the  atmosphere.  The  recoil  ac- 
complishes most  of  the  return  of  the  piston.  During  the  back- 
ward movement  of  the  piston,  the  end  of  the  cylinder  is  open 
to  exhaust  through  slots  /,  in  the  valve  O,  and  groove  /i,  and 
passages  i,j\  k,  until  the  passages  Pand  ^  are  uncovered  by 
the  front  end  of  the  piston,  at  which  time  the  valve  opens,  and, 
admitting  air,  arrests  the  piston  and  drives  it  forward.  Al- 
though communication  between  7' and  7''  is  cut  off  almost  di- 
rectly the  piston  commences  its  backward  movement,  the  valve 
O  will  not  change  its  position — from  rear  to  front — because 
sufficient  air  pressure  is  passing  into  space  c  through  passage  X 
to  hold  the  valve,  notwithstanding  the  escape  of  the  air  via  S, 
since  the  latter  is  of  less  capacity  than  X.     It  will  be  readily 


458 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


understood  that  the  action  of  the  compressed  air  along  the  pas- 
sage G,  acting  first  on  one  area  and  then  on  another  area  of  the 
valve  O,  drives  it  in  alternate  directions,  and  that  the  valve  in 
turn  admits  air  to  either  end  of  the  cylinder;  at  the  same  time 
the  piston  opens  and  closes  certain  ports  in  the  cylinder,  as  in 
the  case  of  the  valveless  hammer,  and  the  combination  of  the 
dual  motions  of  the  valve  and  the  piston  produces  the  desired 
result  of  causing  the  piston  to  rapidly  reciprocate  and  deliver  a 
number  of  blows  upon  the  tool.  In  this  hammer  it  will  be 
noted  that  the  striking  piston  passes  through  the  valve,  which 
has  the  effect  of  increasing  the  stroke  of  the  piston  as  compared 
with   the  original  design  of  the  hammer,  in  which  the  valve 


Fig. 


-THE  TILDF.N   PNEUMATIC  HAMMER. 


was  arranged  in  a  separate  chamber  immediately  in  the  rear  of 
the  piston  chamber,  and  without  increasing  the  over-all  length. 
In  order  to  effect  a  cushion  on  the  piston  on  the  rearward 
stroke,  live  air  is  admitted  before  such  stroke  is  completed. 
With  regard  to  the  valve,  owing  to  its  extreme  lightness  and 
shortness  of  stroke,  cushioning  of  the  valve  is  unnecessary. 

The  Tilden  pneumatic  hammer  is  illustrated  in  section  by 
Fig.  255,  which  shows  the  general  construction  and  also  the 
oil  chamber  in  the  handle,  which  measures  out  and  delivers 
a  constant  supply  of  lubrication  to  the  incoming  air.  The  re- 
ciprocating piston  and  valve  are  thereby  constantly  lubricated, 
a  condition  that  of  course  increases  the  effectiveness  and  dura- 
bility of  the  working  parts.  This  tool  is  manufactured  by  the 
International  Pneumatic  Tool  Company,  of  Chicago. 

The  sectional  view  herewith  grives  an  idea  of  its  construction 


PNEUMATIC    TOOLS.  459 

and  operation.  vStarting  with  the  parts  in  the  position  as  illus- 
trated, the  motive  fluid  or  compressed  air  from  the  main  cham- 
ber passes  through  ports  into  the  valve  block  chamber  to  press 
upon  the  upper  end  extension  of  the  impact  piston,  and  acting 
against  the  decreased  area  thereof  imparts  a  light  initial  move- 
ment to  the  piston,  which  from  practical  experience  is  found  to 
be  very  efficient  in  reducing  the  amount  of  jar  or  vibration. 

Otherwise,  the  air  ports  and  passages  are  similar  in  arrange- 
ment for  operating  the  hammer  piston  as  in  other  direct- 
acting  hammers. 

PNEUMATIC  TOOLS  OF  THE  CHICAGO  PNEUMATIC  TOOL  COMPANY. 

The  "  Xew  Boyer  "  air  hammers  as  now  made  are  the  out- 
come of  several  years  of  experiment  to  overcome  the  vibration 
of  the  older  tools  upon  the  hand  and  arm  of  the  operator, 
when  in  use,  as  well  as  to  simplify  their  construction  and  opera- 
tion. Fig.  256  shows  the  four  sizes  of  their  short-stroke  ham- 
mer as  now^  made,  with  samples  of  chisels  and  calking  tool. 

The  outcome  of  these  trials  is  a  modification  of  the  hammer 
which  greatly  simplifies  the  construction.  The  proportions  of 
certain  operating  parts  have  been  altered  so  that  the  vibration 
is  reduced  to  a  minimum.  The  hammer  is  styled  the  "  New 
Boyer  "  to  distinguish  it  from  the  old  form,  which  is  still  sup- 
plied to  the  trade  if  desired. 

The  general  appearance  and  dimensions  are  not  altered,  the 
difference  being  in  the  operating  valve.  The  valve  mechanism 
of  the  new  hammer  is  entirely  different  from  the  old,  consisting 
of  a  single  moving  part;  namely,  the  valve  itself,  which  is 
formed  of  a  thin  cylindrical  shell  placed  in  the  piston  chamber, 
the  piston  travelling  within  the  valve.  By  this  arrangement  a 
much  longer  piston  chamber  is  obtained,  hence  a  longer  stroke, 
w^ithout  increasing  the  length  of  the  tool;  also,  the  piston  is 
cushioned  at  either  end  of  the  stroke.  With  a  longer  stroke 
the  force  of  the  blows  of  the  piston  is  increased,  and  hence  the 


460 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


new  hammer  has  about  one -third  more  power  than  the  old. 
The  substitution  of  a  simple  piston  valve  for  the  complicated 
arrangement  previously  used  insures  a  longer  life  for  the  ham- 
mer and  fewer  repairs.  The  regulating  mechanism  in  the 
handle  is  not  changed.  For  the  best  working  of  these  ham- 
mers an  air  pressure  of  80  pounds  per  square  inch  is  recom- 
mended, but  they  can  be  operated  with  pressures  varying  from 
20  to  100  pounds. 

These  hammers  are  made  in  four  different  sizes  suitable  for 


ro 


Fig.  256.— 1  he  "new  boyek  "  air  hammers. 


chipping,  stone-carving,  lettering,  or  tracing  on  marble  or 
granite. 

The  Xo.  I  New  Boyer  hammer  weighs  10  pounds,  has  4-inch 
stroke  at  an  estimated  speed  of  2,000  strokes  per  minute,  and 
in  operation  requires  about  20  cubic  feet  of  free  air  per  minute. 
This  hammer  is  especialh'  adapted  to  heavy  work  in  chipping 
and  calking,  and  also  to  light  riveting,  and  has  a  capacity  of 
driving  up  to  |-inch  hot  rivets. 

The  No.  2  New  Boyer  hammer  weighs  9  pounds,  has  3-inch 
stroke  at  an  estimated  speed  of  2,500  strokes  per  minute,  and 


PNEUMATIC    TOOLS.  46  I 

in  operation  requires  about  20  cubic  feet  of  free  air  per  minute. 
This  hammer  is  adapted  to  general  use  in  chipping  in  iron  and 
steel,  and  for  calking  on  ship  and  boiler  work.  For  chipping 
only,  it  is  equipped  with  chisels  having  hexagonal  shanks,  and 
for  calking,  or  for  calking  and  chipping,  where  it  is  desired  to 
use  the  hammer  for  both  purposes,  it  is  equipped  with  chisels 
having  roimd  shanks. 

The  No.  3  New^  Boyer  hammer  weighs  8  pounds,  has  if-inch 
stroke  at  an  estimated  speed  of  3,000  strokes  per  minute,  and 
in  operation  requires  about  20  cubic  feet  of  free  air  per  minute. 
This  hammer  is  especially  adapted  to  beading  locomotive  flues 


Fig.  257.— the  bover  long-sti^oke  riveting  hammer. 

and  to  light  calking.  It  operates  best  at  an  air  pressure  of  75 
to  80  pounds.     Will  bead  two  flues  per  minute. 

The  No.  4  New  Boyer  hammer  weighs  7  pounds,  and  is 
designed  for  very  light  work  such  as  tank  riveting. 

Reputable  concerns  report  that  for  chipping  castings  one 
man  with  a  pneumatic  hammer  does  the  work  formerly  per- 
formed by  three  men.  Fire-boxes  are  cut  out  with  the  aid  of 
these  tools  in  two  and  one-fourth  hours,  where  the  same  work 
was  previously  done  by  contract,  and  eighteen  and  one-half 
hours  allowed,  while  a  total  saving  of  ten  and  one-half  hours  on 
each  fire-box  is  made  by  their  use. 

The  Boyer  long-stroke  hammer  (Fig.  257)  is  adapted  to  all 
kinds  of  rivet  work  up  to  i-inch  diameter  of  rivets.     It  weighs 


462  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

18  pounds,  and  has  a  9-inch  stroke  at  an  estimated  speed  of  800 
strokes  per  minute.  This  is  the  most  powerful  pneumatic 
hammer  made,  and  will  meet  the  most  difficult  requirements. 

The  new  No.  o  long-stroke  hammer  of  this  company  weighs 
13  pounds,  and  has  a  5 -inch  stroke  with  an  estimated  speed  of 


Fig.  25S.— the  pneumatic  hold-on. 

1,800  blows  per  minute.      Its  most  useful  work  is  in  chipping 
and  driving  rivets  up  to  -|  inch. 

The  hold-on  (Fig.  258)  has  a  piston  and  pressure  air  spring, 
and  is  also  provided  with  an  extension  bar  to  hold  it  in  position 
in  confined  places. 

THE    PNEUMATIC    HAMMER    AND    ITS    WORK    IN    STONE     DRESSING. 

Perhaps  the  most  marked  improvement  in  the  stonecutter's 
art  since  the  stone  age  has  been  the  introduction  of  the  use  of 
compressed  air.  For  centuries  the  hard,  unyielding  stone  had 
been  fashioned  into  shape  by  the  ceaseless  efforts  of  the  ham- 
mer and  chisel;  and  while  other  trades  adopted  newer  and 
cheaper  methods  of  manufacture  in  rapid  succession,  no  means 
could  be  devised  to  hasten  the  tedious  processes  of  stone-cutting. 

The  arm  of  the  carver  could  deliver  only  a  comparatively 
small  number  of  blows  per  minute,  but  by  the  use  of  pneumatic 
carving  tools  this  number  was  multiplied  to  such  an  extent  that 
the  blows  following  each  other  in  rapid  succession  are  in  effect 
one  continuous  blow. 


PNEUMATIC    TOOLS. 


463 


As  the  cutting  power  is  always  ready,  the  carver  had  merely 
to  guide  the  machine  and  chisel.  He  can  thus  give  his  whole 
attention  to  his  work,  and  the  result  is  shown  in  the  increased 
amount  of  work  accomplished,  and  the  work  is  done  much 
better. 

A  machine  for  surfacing  granite  and  other  hard  stone  is  in 
use  in  which  a  pov/erful  pneumatic  hammer  is  mounted  on  a 
radial  arm,  which  is  in  turn  supported  on  a  vertical  column  or 


Fig.  259.— the  pneumatic  hammer  i.\  stone  dressing. 

post,  and  is  moved  in  a  plane  for  the  operation  of  the  dressing 
tool  in  any  required  direction. 


THE    PNEUMATIC    HAMMER    AND    ITS    WORK    IN    SCULPTURE. 

The  beautiful  work  of  the  sculpture's  art  has  now  a  hand- 
maid in  the  pneumatic  tool,  which  is  achieving  wonders  in  the 
rapidity  of  its  producing  power.  The  relief  to  the  weary  arm  is 
a  helper  to  artistic  thought,  and  the  labor  of  the  artist  does  not 
hang  heavy  on  his  mind.  In  this  way,  modern  sculpture  should 
not  only  advance  in  its  output  of  volume,  but  should  rise  to  a 


464 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


higher  degree  of  perfection  by  the  relief  from  irksome  muscu- 
lar labor,  and  freedom  of  mind  for  the  inception  of  beauty  of 
thought  and  its  transfer  to  the  rigor  of  stone. 


Fig.  260.— the  pneumatic  hammer  in  sculpture. 


THE    PNEUMATIC    HAMMER    IN   THE    PATTERN    SHOP. 

A  Pneumatic  Fret-Saw. — There  has  recently  been  made  a 
new  and  interesting  application  of  the  pneumatic  tool.  This  is 
a  fret-saw  directly  attached  to  the  piston  of  a  pneumatic  ham- 
mer and  making  from  1,000  to  1,800  strokes  per  minute.  The 
saw  is  an  ordinary  keyhole-saw  blade,  and  it  may  be  made  to 
follow  the  most  difficult  lines,  of  course  cutting  rapidly.  Be- 
sides the  evident  use  of  the  tool  for  the  patternmaker  and  the 
cabinetmaker,  it  may  be  noted  that  it  is  employed  in  one  of  the 
largest  packing-houses  in  Chicago  for  sawing  ham  bones,  using 
a  special  saw  with  very  fine  teeth.  This  device  has  recently 
been  brought  out  by  the  Chicago  Pneumatic  Tool  Company. 


PNEUMATIC    TOOLS. 


465 


Fig.  261.— pneumatic  fret  saw. 
THE    PNEUMATIC    HAMMER    IN    THE    MACHINE    SHOP. 

Probably  in  no  place  else  can  the  pneumatic  hammer,  and 
also  the  pneumatic  drill,  be  applied  to  so  many  and  so  varied 
classes  of  work  as  in  the  machine  shop.     A  line  of  air  pipe 


Fig.  262. —the  pneumatic  ham-mek  in  the  machine  shop. 


30 


466 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


along  the  ceiling  over  the  vice-benches,  with  the  air  hose  at- 
tached to  a  hammer  and  a  drill,  standing  upon  the  bench, 
ready  for  instant  use,  is  the  modern  exemplification  of  economy 
in  the  production  of  machinery  and  manufactured  goods,  that 
has  given  the  Western  world  an  advanced  position  in  the  pro- 
duction and  distribution  of  machinery  used  in  the  producing 
industry  of  all  nations. 

THE    WORK    OF    PNEUMATIC    TOOLS. 


Fig.  263.— the  boyer  air  drill  in  >hii'  work. 
Held  up  on  skids.     On  frame  for  bottom  drilling. 


The  following  illustrations  show  methods  of  using  pneu- 
matic tools  in  the  various  parts  of  the  constructive  work  in  ship- 
building; to  these  tools  our  steel  ship-building  interests  owe 
much  of  their  competitive  success. 


THE    WORK    OF    PNEUMATIC    TOOLS. 


467 


468 


COMPKESSKD    AIR    AND    ITS    ATPLICATIONS. 


-     "   ^ 


N 


THE    WORK    OF    PNEUMATIC   TOOLS. 


469 


Fig.  26S.— riveting  frames  at  the  wcikks. 


Fig.  20U.-THE  lonl,-;. .......  ..uver  i.\  shii'  work. 


470 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


THE    PNEUMATIC    HAMMER    AND    DRILL    IN    SHIP-BUILDING. 


The  air  hammer  as  a  riveter  on  a  balanced  transverse  beam 

with  a  ratchet  stay  or  guide,  is 
one  of  the  late  appliances  for 
holding  and  steadying  the 
hammer  in  deck  riveting, 
and  is  illustrated  in' Fig.  270, 
while  its  method  of  operation 

Fig.  270. -the  balanck  beam.  ^g  shown  in  Ficr.  27  I. 

It  is  one  of  the  handy  devices  lately  invented  for  the  rapid 
work  of  deck  riveting  and  for  relieving  the  m.uscular  effort  of 
holding  the  hammer  in  constant  and  continuous  work. 


Fig.  271.— the  balance  beam  in  deck  riveting. 


THE    WORK    OF    PNEUMATIC    TOOLS. 


471 


Fig.  272.— drilling  axd  riveting  in  shu'-ijuilding. 


Fig.  273.— the  rivet  hammer  and  hold-on  in  bulkhead  work. 


472 


COMPRESSED    AIR    AND    ITS    API'I.ICATIONS. 


"'Cli^'v 

\ 

^V^^%L 

m 

I- ==^... 

t~^ 

1 

S 

Fig.  274.— strlctukal  ki\eti: 


Fig.  275.— the  yoke  riveter. 


Fig.  276.— the  long  yoke  riveter. 


THE    WORK    OF   PNEUMATIC   TOOLS.  473 


THE    BOYER    RIVETER    IN    STRUCTURAL    WORK. 

No  Other  improvement  in  the  means  of  erection  of  modern 
structural  work  is  so  convenient  and  so  economical  as  are 
compressed  air  tools.  The  air  hammer  and  its  mate,  the  air 
drill,  have  come  to  meet  the  needs  of  the  times  for  quick  work. 
This  wonderful  saving  in  time,  which  is  a  most  important  ele- 
ment in  the  erection  of  the  great  steel  structures  of  modern 
days,  has  given  an  impulse  to  this  class  of  structure  that  is  felt 
throughout  the  civilized  world,  a  marvel  to  all  nations. 

Probably  no  other  class  of  construction  tools  has  comein  to 
use  in  a  single  decade,  that  has  contributed  so  large  a  share  to 
the  relief  of  muscular  labor  in  the  new  method  of  building  with 
steel  interframing,  as  the  compressed-air  tools.  Their  porta- 
bility and  the  later  methods  of  compressing  air  by  portable 
compressors  have  gone  hand  in  hand  in  this  progressive  age  of 
building. 

THE    CHICAGO    COMPRESSION    RIVETER. 

The  compression  riveters,  Figs.  277  to  280,  are  unique 
tools  for  their  special  work.  They  embody  in  a  compact  form 
their  own  hold-on,  and  are  operated  by  an  air  piston  of  large 
area  pressing  upon  a  hydraulic  piston  of  small  area,  which 
pressure  is  transferred  to  the  piston  of  the  riveting  plunger 
at  right  angles,  thus  generating  the  immense  pressure  required 
to  compress  a  rivet  at  one  stroke.  These  compact  and  power- 
ful tools  are  hung  and  balanced  on  yoke  slings  and  are  easily 
managed  in  any  position.  The  transfer  medium  between  the 
right-angled  pistons  is  oil  with  cupped  leather  packings  on  the 
pistons. 


474 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


THE    WORK    OP^    PNEUMATIC   TOOLS. 


475 


am  ■iiimiiiiiiimi  n  mmJ^^^^  ^V^H^^^^^^^^V 


2     " 


476 


COMPRKSSED   AIR   AND    ITS   APPLICATIONS. 


Fig.  2S1.— calking  a  large  water  pipe. 


Fig.  282.— ri\-etixg  with  the  ealanxe  attachme.xt. 


THE    WORK    OF    PNEUMATIC    TOOLS. 


477 


4/8  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


I'Ki.    285. — LON'G-STROKE   HAMMER    AND   HOLD-ON    IN    BOILER   WORK. 


Fig.  2S6.— loxg-stroke  hammer  and  hold-on  in  structural  work. 


PNEUMATIC    TOOLS. 


479 


COMPRESSED    AIR    DRILLS    AND    THEIR    WORK. 

The  simple  rotary  air  drill  for  hand  use  commends  itself  as 
one  among  the  handy  tools  of  a  shop.  It  may  consist  of  a 
rotary  air  motor  fixed  to  the  drill  spindle,  in  a  case  to  which 
the  handles  and  breastplate  are  attached.  Compressed  air  en- 
ters through  the  handle  with  the  valve  lever  and  is  exhausted 
through  the  opposite  handle. 

Another  form  of  rotary  air  motor  drill  stock,  with  simple 
blades  held  to  the  cylinder  and  central  over  the  drill  spindle, 
is  illustrated  on  page  488. 
The  motor  journals  termi 
nate  in  a  small  bevel  pinion 
that  meshes  in  a  ring  gear 
attached  by  the  lower  sec- 
tion of  the  case  to  the  drill 
spindle,  the  handles  being 
attached  to  the  upper  or 
motor  section  of  the  case. 

In  Fig.  287  is  shown  the  vertical  section  of  an  oscillating 
piston  drill,  in  which  one  of  the  cylinders  and  trunnions  is 
shown  at  the  right,  in  the  trunnions  of  which  are  placed  the 
inlet  and  exhaust  port.  The  air  enters  the  revolving  central 
spindle  through  the  small  holes  shown  in  the  hollow  spindle 
and  is  delivered  to  the  oscillating  trunnion  through  the  lower 
hole  in  the  hollow  part  of  the  spindle. 

In  Fig.  288  are  represented  the  outside  view,  the  horizontal 
section,  and  the  vertical  section  of  a  Haesler  pneumatic  drill. 
It  is  operated  by  four  pistons  in  two  cylinders,  double-acting. 
The  piston  rods  have  a  jointed  connection  to  cam  cranks  on  the 
pinion  shafts.  The  piston  valves  are  operated  by  levers  pivoted 
to  opposite  piston  rods,  as  shown  in  the  horizontal  section. 
The  pistons  act  alternately  in  the  cylinders  so  that  there  is  no 
dead  centre.  The  large  spur  wheel  is  attached  to  the  spindle 
and  revolves  with  it. 


Fig.  287.— vertical  section. 


48o 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


<f^^OT^rf39^ 


THE   HAESLER   DRILL. 


In  Fig.  289  are  shown  a 
vertical  view  and  a  sectional 
plan  of  a  three-cylinder  os- 
cillating motor  drill.  The 
compressed  air  enters 
through  one  of  the  handles, 
its  flow  being  controlled  by 
a  lever  and  valve.  The  ex- 
haust enters  the  case  from 
the  port  in  the  oscillating 
cylinder  trunnions.  The 
three  double-acting  pistons 
are  directly  connected  to 
cranks  and  pinions  which 
mesh  with  an  internal  spur 
gear,  which  is  fast  to  the 
outer  shell.  The  spider 
which  carries  the  cylinders  and  pinions  is  fast  on  the  central 
spindle  and  revolves  with  it.  The  inlet  and  exhaust  ports 
are  shown  in  the  horizontal  section  of  the  top  trunnion  at  A. 

In  the  succeeding  illus- 
trations are  shown  some  of 
the  standard  types  of  pneu- 
matic drills.  Fig.  290  is  a 
longitudinal  sectional  eleva- 
tion of  a  "  Little  Giant  "  port- 
able air  drill,  taken  on  the 
central  line  i  —  i  of  the  hori- 
zontal section  (Fig.  291). 

In  this  type  of  drill  the 
motor  consists  of  four  single- 
acting  cylinders  arranged  in 
pairs,  and  having  each  pair 
of  pistons  connected  to  op- 
posite    ends     of    a    double  pic.  289.-THE  piston  drilu 


PNEUMATIC    TOOLS. 


481 


Fig.  290.— little  giant,  sectional  elev-ation. 


crank-shaft.     The  pistons  of  each  pair  travel  in  opposite  direc- 
tions at  all  parts  of  the  stroke  to  effect  smooth  running.     The 

cylinders  are  controlled  by 
balanced  piston  valves  set  to 
cut  off  at  five-eighths  of 
the  stroke,  and  should  there- 
fore prove  economical.  Re- 
ferring to  Figs.  290  and 
291,  A  is  the  main  casing, 
which  contains  the  mechan- 
ism ;  B  and  B '  are  one  pair 
of  cylinders,  and  C  and  C 
are  the  other,  arranged  at 
right  angles  to  each  other 
and  connected  to  a  common 
crank  shaft  D.  By  this  ar- 
ranpfement  a  dead  centre  is  avoided.  The  air  admission  and 
exhaust  are  controlled  by  two  piston  valves,  E  and  E\  These 
are  worked  by  small  eccentrics  off  the  crank  shaft,  and  serve 
to  control  the  four  cylinders ;  /  is  the  main  pressure  chamber, 
having  communication  with 
the  supply  pipe  H.  The 
arrows  show  the  direction 
taken  by  the  air.  Cylinders 
B  and  B '  receive  air  com- 
munication through  /'  and 
/',  and  cylinders  B  and  j5  ' 
through  c"  and  c\  the  exhaust 
taking  place  through  the  in- 
terior of  the  two  valves. 
The  action   is  as  follows:  /     P'«-   ^9r-uTTLE   giant,  section   through 

■^  CYLINDERS. 

is   full  of  live  air  which   is 

blowing  through  c'  and/',  to  supply  cylinders  C  and  C\  while 
cylinders  B  and  B '  are  exhausting  through  /'  and  c"  into  the 
centre  of  the  valves,  and  thus  to  the  atmosphere.     Referring  to 
31 


I  — 


482 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Fig.  292.— little  giaxt,  high  speed. 


Fig.  290,  /•  and  /-'  are  gear  wheels  by  which  the  rotary  motion 
of  the  crank-shaft  is  conveyed  to  the  part  K,  which  is  fitted 

with  a  suitable  drill-holder  or 
chuck.  L  is  a  threaded 
sleeve,  which,  in  conjunction 
with  IJ  and  other  parts,  pro- 
vides for  feeding  the  drill. 
This  tool  is  also  furnished 
with  a  simple  reversing  ar- 
rangement, which  enables  it 
to  do  all  classes  of  work  for  which  a  drill  is  suitable ;  for  this 
it  is  fitted  with  a  handle  in  the  place  of  the  star  centre.  By 
revolving  this  handle  a  valve  placed  in  the  main  pressure 
chamber  reverses  the  direction  taken  by  the  air  when  entering 
the  valve  bushing,  suitable  ports  being  provided. 

Figs.  292  and  293  illustrate  the  "  Little  Giant "  high-speed 
rotary  drill,  which  consists  of  a  casing  C  containing  three  rotat- 
ing cylinders  F^  each  of  which  is  governed  by  a  piston  slide 
valve  E.  These  valves  rotate  with  and  work  in  cylinders  or 
valve  chambers  forming  part  of  the  main  engine  cylinders  F. 
In  other  machines  for  effecting  the  same  and  similar  purposes 


Fig.  20^,,— little  giant  fixed  cylinders. 


the  casing  is  used  as  a  live-air  chamber;  in  the  "  Little  Giant  " 
type  it  is  used  as  an  exhaust  receiver.  Again,  in  other 
machines  the    air    is  directly  admitted    into   the  casing    C  or 


PNEUMATIC    TOOLS. 


483 


live-air  chamber,  whereas  with  the  "  Little  Giant  "  drill  it  is 
carried  through  a  separate  channel  from  the  supply  pipe  A, 
and  through  a  stationary  or  fixed  hollow  crank-shaft  B,  into  a 
passage  L,  leading  to  the  reduced  portions  of  the  piston  slide 
valves  £,  and  according  to  the  position  of  such  valves  admitted 
to,  or  exhausted  from,  the  cylinders  F.  It  will  also  be  noticed 
that  in  the  "  Little  Giant  " 
drill  the  exhaust  does  not 
blow  through  the  gear 
mechanism,  since  it  is  so 
arranged  that  it  is  admit- 
ted into  the  main  casing  C, 
which  is  itself  sealed  from 
the  lower  portion  of  the 
machine,  containing  the 
reducing  gear,  so  that  the 
exhaust  passes  out  through 
a  separate  pipe  K. 

The  leading  feature  in 
the  "  Little  Giant  "  machine 
is  that  it  combines  a  high- 
speed engine  with  a  low 
consumption  of  air,  and 
this  result  has  been  ob- 
tained by  employing  a  stationary  eccentric,  which  is  set  at  the 
required  point  in  the  throw  of  the  crank  to  obtain  the  neces- 
sary cut-off,  the  cylinders  F,  and  their  governing  slide  valves  £, 
rotating  about  this  eccentric.  As  is  well  known,  in  engines  of 
this  type  the  travel  of  the  eccentric  should  be  quickest  when 
the  motion  of  the  piston  is  slowest,  and  this  is  provided  for  in 
the  design  by  having  a  very  quick  port  opening  and  an  equally 
quick  release,  thus  enabling  the  rotating  cylinders  to  move  at 
an  exceedingly  rapid  rate,  the  air  not  having  to  travel  through 
tortuous  passages  either  in  or  out. 

Fig.    294    illustrates    a    transverse    vertical    section    of    a 


Fig.  294.— section,  boyer  drill. 


484 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


"  Boyer  "  piston  drill,  and  Fig.  295  is  a  horizontal  section  taken 
through  the  centre  of  the  cylinders.  The  machine  consists  of 
three  main  parts  :  (i)  The  upper  housing  into  which  the 
throttle  valve  and  steadying  handle  are  screwed,  and  which 
forms  a  live-air  chamber  carrying  the  motor;  (2)  the  diaphragm 
which  forms  the  lid  or  cover  of  the  upper  housing  or  live-air 
chamber,  and  through  which  the  hollow  exhaust  spindle  pro- 
jects; (3)  the  lower  housing  secured  to  the  upper  housing  by 
means  of  screws,  and  containing  the  gear-wheel  rack  bearings 
for  drill  spindle,  etc.  The  motor  is  in  the  form  of  a  three- 
cylinder  single-acting  oscillating  engine,  the  cylinders  being 

carried  in  the  rotary  frame. 
This  frame  consists  of  an  up- 
per and  a  lower  plate,  and  is  tri- 
angular in  shape  and  free  to 
revolve  round  its  centre  on  two 
bearings,  the  lower  one  being 
a  hollow  shaft,  connected  by 
gearing  to  an  internally  toothed 
wheel  in  the  lower  half  of  the 
casing.  The  admission  of  air 
to  the  cylinders  is  regulated  by  the  valves  formed  in  the  pivots 
upon  which  the  cylinders  oscillate.  The  cylinders  are  single 
acting,  and  the  inner  ends  are  open ;  therefore  air  under  press- 
ure, of  which  the  upper  casing  is  always  full,  has  free  ac- 
cess to  the  pistons  on  that  side.  It  would  seem,  therefore, 
that  air  being  admitted  through  the  pivot  valves  would  only 
produce  equilibrium ;  but  since  one  of  the  cylinders  is  always 
open  to  the  exhaust  through  the  hollow  bearing  of  the  triangu- 
lar frame,  this  equilibrium  becomes  disturbed,  and  the  com- 
pressed air  has  full  effect  upon  each  piston  as  the  valve  comes 
in  line  with  the  exhaust.  The  cylinders  are  constructed  of 
steel  tubes,  and  are  fitted  with  trunk  pistons  having  their  con- 
necting-rod ends  attached  to  a  fixed  crank-pin  common  to  them 
all.     The    pistons    are    set  in  motion    by   the    introduction    of 


Fig.  295.— horizontal  section,  boyer. 


PNEUMATIC   TOOLS. 


485 


compressed  air  into  the  upper  casing  and  into  the  cylinder  as 
already  described ;  this  has  the  effect  of  causing  the  three  cylin- 
ders, together  with  their  triangular  framing,  to  rotate  round 
the  fixed  crank  pin,  and  thus  transmits  rotary  motion  to  the 
spindle  by  means  of  the  gearing  before  referred  to.     This  class 


ka^^ 


^^^M 


Fig.  296.— the  whitelaw  drill. 


of  machine  is  fitted  with  a  regulator  by  means  of  which  the 
power  and  speed  of  the  drill  can  be  varied  as  desired. 

Fig.  296  shows  the  interior  of  a  "Whitelaw  "  reversible  drill 
wnth  half  the  casing  removed,  showing  the  piston  valve  /and 
the  passage  of  the  air  leading  to  the  cylinder  and  the  method 
of  reversal.     This  type  of  drill  is  actuated  by  two  double-acting 


486 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


oscillating  cylinders  ^l  and  B,  driving  a  crank  shaft  C,  to  which 
is  attached  a  pinion  D  driving  the  gear  wheel  /f,  attached  to 
the  drill  spindle.  Its  action  is  therefore  at  once  apparent; 
for  by  rotating  the  milled  handle  I\  which  gears  into  the 
short  rack  G  at  the  end  of  the  lever  N,  the  hollow  portion  of 
the  piston  valve  /changes  its  position,  with  the  result  that  re- 
vensal  takes  place  in  the  usual  way  adopted  in  oscillating  cylin- 
ders. The  exhaust  is  made  into  the  casing  and  escapes  through 
suitable  apertures.  The  reversal  is  instantaneous,  and  the 
machine  is  well  adapted  for  all  kinds  of  drilling,  tapping,  tube- 


FlG.   297.— THE  BOYER   PISTON   AIR   DRILL. 

expanding,  wood-boring,  etc.,  the  reversing  arrangement  espe- 
cially lending  itself  to  such  purposes.  The  machine  is  sup- 
plied with  ample  lubrication,  and  is  fitted  with  ball  bearings 
throughout. 

The  Boyer  piston  air  drill  is  of  the  three-piston  type,  and  is 
adapted  for  drilling  iron  and  steel  up  to  three  inches  in  diameter 
(Fig.  297).  It  is  used  extensively  in  boiler  shops,  shipbuilding 
concerns,  machine  shops,  architectural  works,  foundries,  etc. 
Many  appliances  are  used  in  connection  with  these  drills,  such 
as  flue  rollers,  grinding-chucks,  flue  cutters,  stay-bolt  cutters, 
and  side-light  cutters. 

Fig.  298  shows  the  method  of  driving  countersunk  flush 
rivets  on  the  bottom  of  a  vessel  by  compressed  air.      The  small 


PNEUMATIC    TOOLS. 


487 


hammer  seen  in  the  ilhistration  is  used  for  chipping  the  head 
of  the  rivet  smooth,  and  the  drill  is  used  to  ream  the  rivet  holes 
to  a  sufficient  diameter  to  receive  the  rivet. 

The  pneumatic  rotary  motor  drill  stock  consists  of  a  hori- 
zontal rotary  motor,  over  the  centre  of  the  spindle,  having  on 
one  end  of  its  shaft  a  bevel  pinion,  which  drives  a  bevel  gear 


29S. 


THE   PNEUMATIC   DRILL  AND   HAMMER   IN   SHIP  WORK. 


attached  by  the  lower  section  of  the  case  to  the  drill  spindle. 
The  inlet  and  exhaust  ports  and  valves  are  shown  in  the  verti- 
cal section. 

The  rotary  drill,  as  shown  in  Figs.  300-302,  is  the  early 
type  of  pneumatic  drill,  and  is  still  extensively  used  on  heavy 
drilling  and  reaming.  Its  simplicity  of  construction  and  small 
number  of  working  parts  give  it  some  advantages  over  the  more 
complicated  types  of  air  drills. 


488 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


Fig.  299.— the  phcenix  rotary  air  drill. 


Fig.  300.— rotary  breast  drill.      Fig.  301.— the  rotary.  Fig.  302— section. 


Fig.  303.— the  light  breast'drill. 


PNEUMATIC    TOOLS. 


489 


The  Chicago  breast  drill  is  of  the  oscillating  cylinder  type, 
and  is  capable  of  drilling  up  to  ^  inch  in  iron  or  steel.  It  is 
an  invaluable  tool  where  a  large  number  of  small  holes  are  to 
be  bored.     It  is  used  for  wood-boring  with  equal  success. 

Fig-  303  ^^  ^n  illustration  of  the  Chicago  rotary  breast 
drill,  a  very  light,  compact  drill  capable  of  drilling  up  to  f  inch 
in  metal. 

Fig.  304  is  a  larger-sized  drill  of  the  same  type  as  in  the  pre- 
ceding illustration,  and  is  adapted  for  drilling  up  to  ^  inch  in 


:^.  t 


MAJL 


Fig.   304. — THE    MEDIUM   BREAS  1'   DRILL. 

Weight,  five  pounds. 

metal,  and  also  for  light  wood-boring.  It  can  be  used  with  feed 
screw.  It  is  employed  in  shops  having  a  lighter  grade  of  work 
both  in  iron  and  brass;  also  in  wood-working  establishments, 
in  the  building  of  small  wooden  vessels,  where  a  great  number 
of  small  holes  are  to  be  bored. 

The  Whitelaw  types  of  reversible  drills  are  for  all  kinds  of 
wood-boring.  They  are  used  extensively  in  car  shops,  wood 
ship3'ards,  etc. ;  are  very  light,  and  will  bore  up  to  four  inches 
diameter  in  about  one-fifth  the  time  required  by  hand  methods. 


490  COMPRESSED    AIR   AND    ITS   ArPLICATIONS. 


Fig.  305.— the  CHICAGO  breast  drill. 


PNEUMATIC    TOOLS. 


491 


# 


Fig.  306. -whitelaw  reversible  drill. 


/K 

CK^ 

RH^^^^^Bt '^ -^^Si 

Fig.  307.— whitelaw  reversible  wood-boring  drill. 
Weighs  ten  pounds,  and  wiil  bore  up  to  four  inches  diameter. 


492 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


J     ^ 


THE    WORK    OF    TNEUMATIC    TOOLS. 


493 


-    a 


-   e 


494 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


s     S 


THE    WORK    OF    PNEUMATIC    TOOLS. 


493 


496  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Fig.  316.— drilling  and  riveting  with  pneumatic  tools. 


Fig.  317.— drilling  manhole  in  a  tank. 


Chapter  XXIV. 


PNEUMATIC  TOOLS— Continued 


PNEUMATIC    TOOLS. 

{Continued.) 

PNEUMATIC    HAMMERS    OF    THE    Q.    &    C.    COMPANY, 
NEW    YORK    CITY. 

The  hammers  of  this  company  are  made  in  four  sizes,  and 
are  used  with  pressures  of  from  80  to  90  pounds  for  their  best 
work.  Fig.  318  shows  this  hammer  in  section,  consisting  of  a 
differential  cylinder  case  containing  the  air  passages  for  press- 


FlG.   318.— SECTION   OF  THE   Q.   cS:  C.    HAMMER. 

ure  and  return  stroke,  and  the  relief  chamber  and  exhaust 
port.  In  the  handle  the  spring-closed  air  valve  and  thumb 
lever  are  plainly  shown.  The  piston  has  a  differential  action  in 
which  the  annular  chamber  due  to  its  enlarged  upper  section 
allows  the  up-stroke  to  be  made  with  a  small  piston  area  sub- 
ject to  pressure,  and  a  much  greater  area  on  the  down-stroke  for 
its  greater  work.  The  piston  has  a  hollow  centre  leading  to  a 
side  port,  which  exhausts  the  down-air  pressure  at  the  moment 
of  closing  the  inlet  port  and  simultaneous  with  its  impact  with 


500 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


the  tool  or  chisel.     The  piston  is  returned  by  the  pressure  in 
the  annular  section. 

In  Fig.  319  is  shown  a  lettered  section  of  the  Q.  &,  C. 
pneumatic  hammer,  the  basis  of  construction  of  which  is  the 
Johnson  patent.  The  small  globular  chamber  A,  together  with 
the  conical  chamber  in  the  piston,  is  charged  with  compressed 
air  at  the  moment  the  air  port  5  reaches  the  inlet  space  Po, 
when  the  elasticity  of  the  air  in  the  chamber  carries  the  piston 
forward,  closing  the  inlet  port  and  pushing  the  piston  to  its 
stroke,  when  the  air  is  exhausted  at  the  chamber  and  port  £. 
7^  is  the  flexible  hose  connection,  and  7"  the  air-valve  trip.     The 


Fig.  319.— section  of  q.  &  c.  hammer. 

air  enters  in  the  direction  of  the  arrows  in  the  cut  and  into  the 
annular  section  of  the  cylinder  and  piston,  lifting  the  piston 
to  the  top  position  of  the  stroke,  when  the  piston  ports  open  to 
the  annular  chamber  and  the  full  air  pressure  is  thrown  against 
the  piston. 

The  diameters  of  the  four  smaller  sizes  of  pistons  are  respec- 
tively i^  and  i^  inches;  stroke,  i,  i,  and  2  inches;  weight,  ^, 
f,  I,  i^  pounds,  making  from  1,500  to  2, 500 strokes  per  minute. 
From  the  known  weight  of  the  piston,  length  of  stroke,  and 
number  of  strokes  made  per  minute,  the  force  of  the  hammer 
blow  may  be  computed  by  formulas  given  on  another  page. 

Although  these  hammers,  with  their  smaller-sized  pistons, 
when  compared  with  a  machinist's  hammer  or  the  mallet  of  the 
stone-cutter,  seem  very  light  for  effective  work,  yet  their  light 
weight  is  in  a  great  measure  compensated  for  by  their  velocity 


PNEUMATIC    TOOLS.  501 

of  about  30  feet  per  second  at  the  moment  of  impact.  This  ve- 
locity, with  a  pressure  of  from  50  to  100  pounds  behind  it,  pro- 
duces a  result  that  is  fully  equivalent  to  the  ordinary  blow  from 
a  much  heavier  hand-hammer. 

Fig.  320  shows  the  manner  of  holding  the  hammer  and 
chisel  in  chipping  plate  work.  Fig.  321  is  a  stone-carving  ham- 
mer, the  form  of  which  is 
required  to  adapt  its  posi- 
tion quickly  to  variable 
surfaces.  It  is  held  by  the 
cylinder  in  one  hand  with 
the  thumb  on  the  knurled 
adjusting  screw,  while  the 
other  hand  guides  the 
chisel. 

Riveters      with       yoke 
frames    of  various   dimen- 
sions, and  fitted  with  pneu- 
matic hold-on,  have  many 
advantages    when    provid- 
ed with  claw   compressors 
around  the   riveting  ham- 
mer to  hold  the  rivet-head  hard  against  the  plate  and  to  keep 
the  plates  tight  together  by  pressure  of  the  piston  of  the  hold- 
on.     The  claw  is  seen  in  the  cut  at  the  right  around  the  ham- 
mer, Fig.  322.  V 

When  the  riveter  is  placed  over  a  rivet,  the  air  valve  at  the 
left  in  the  cut  is  opened,  and  air  pressure,  which  may  be  200  or 
more  pounds  according  to  the  area  of  the  piston,  pushes  the 
head  of  the  rivet  and  the  plates  tight  against  the  hammer  claw; 
then  by  opening  the  valve  at  the  right-hand  side,  the  hammer 
is  operated  with  the  full  force  of  the  air  pressure. 

Fig.  323  shows  the  method  of  suspending  a  yoke  riveter  for 
a  free  set  in  any  angular  position.  The  point  of  suspension  is 
at  the  centre  of  gravity,  so  that  the  riveter  is  easily  held  in  any 


;02 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  321.— stone-carving  hammer. 


Fig.  322.— yoke  riveter. 


PNEUMATIC    TOOLS. 


503 


desired  position.  In  this  type  the  cylinder  of  the  striking 
hammer  is  advanced  to  catch  the  end  of  the  rivet  by  sliding 
forward  in  the  outer  shell  at  the  same  moment  that  the  ham- 


FlG.   323.— VOKE-RIVETER  SUSPENSION. 

mer  begins  to  operate,  and  is  held  there  by  the  same  pressure 
that  operates  the  hammer. 

The  bar-yoke  riveter  may  be  suspended  for  vertical  work; 
it  being  a  universal  suspension  arrangement  by  which  any 
position  may  be  obtained  by  a  mere  change  in  the  socket  hold. 
This  class  of  riveters  above  30-inch  gap  are  made  with  pipe 
frames  up  to  6  or  more  feet  gap,  with  varying  openings  from 
10  to  14  inches,  or  more  if  desired. 


504  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


Fig.  324  —section  of  mov^ing  parts  of  voKii  kivetek. 
The  cushion  hold-on. 


Fig.  325.— section  of  solid  head  a.nu  momng  tarts  of  voke  i<i\  kter  (q.  &  c.  co.) 


PNEUMATIC   TOOLS. 


505 


Fig.  326.— stationarv  kivkter. 


Fig.  327. -piston  pnp-.umatic  drill. 


5o6 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


In  Fig.  326  is  represented  a  stationary  riveter  with  a  differ- 
ential piston  which  closes  upon  the  plates  and  rivet-head  with 
great  pressure,  when  the  hammer  piston  finishes  the  work  of 
riveting.  The  three-way  valve  at  the  left  above  the  cylinder 
gives  full  air  pressure  at  the  back  of  the  push  piston  and  oper- 
ates the  hammer  piston.  By  its  reversion  it  becomes  the  ex- 
haust port,  and  by  opening 
the  right-hand  valve  the 
push  piston  is  withdrawn. 

The  pneumatic  drills  of 
the  Q.  &  C.  Company  are 
illustrated  in  Fig.  327, 
showing  the  construction, 
which  consists  of  four  pis- 
tons, single-acting,  con- 
nected in  pairs  to  two 
crank  shafts  with  pinions, 
meshed  in  a  larger  driven 
gear,  which  carries  the 
drill.  Each  crank  shaft 
operates  piston  valves  to  its 
pair  of  cylinders  and  is  set 
at  three-fourths  cut-off.  The  air  inlet  is  regulated  by  twisting 
the  sleeve  on  the  hose  handle,  called  a  rotary  throttle.  Two 
sizes  are  made,  of  40  and  28  pounds  weight,  which  will  drill 
holes  of  2|-  and  i^  inches  respectivel5\ 

Fig.  328  represents  the  reversible  drill  of  the  Q.  &  C.  Com- 
pany, for  wood-boring  and  light  metal  work.  It  is  of  the  same 
general  construction  as  their  heavier  drills,  but  is  valveless,  as 
the  pistons  control  the  air  passages.  There  are  two  spindles 
for  high  and  low  speeds,  and  by  means  of  a  special  chuck  the 
tool  can  be  quickly  changed  from  one  spindle  to  the  other. 
The  drill  is  reversed  by  a  small  lever  separate  from  the  handle. 
The  handle  at  the  top  can  be  replaced  by  a  breastplate  or  a 
feed-screw,  shown  in  the  illustration. 


Fig.  328.— drill  at  work. 


PNEUMATIC    TOOLS.  507 


PNEUMATIC    TOOLS    OF   THE    STANDARD    RAILWAY    EQUIPMENT 
COMPANY,    ST.    LOUIS,    MO. — HAMMERS. 

The  "  AA"  Monarch  hammer  has  a  i-inch  diameter  piston. 
The  stroke  is  also  i  inch,  and  the  hammer  runs  at  an  estimated 
speed  of  2,800  strokes  per  minute.  Weighs  9^  pounds  and  is 
best  adapted  for  light  calking  and  chipping. 

The  "A"  Monarch  hammer  has  a  i-inch  diameter  piston, 
the  stroke  is  if  inches;  this  hammer  runs  at  an  estimated  speed 
of  2,300  strokes  per  minute.  Weighs  loi-  pounds,  and  is  espe- 
cially desirable  for  general  use  in  boiler  shops  and  foundries, 
for  chipping  iron  and  steel,  calking  on  boilers,  and  beading 
flues. 

The  "B"  Monarch  hammer  has  a  i-inch  diameter  piston, 
and  the  stroke  is  2^  inches ;  it  runs  at  an  estimated  speed  of 
2,000  strokes  per  minute.  Weighs  12  pounds.  It  is  best 
adapted  for  heavy  chipping,  such  as  steel  castings,  boiler 
plates,  and  light  riveting. 

The  consumption  of  air  for  these  tools  is  from  15  to  18  cubic 
feet  of  free  air  per  minute,  and  they  operate  best  at  a  working 
pressure  of  from  80  to  100  pounds. 

Their  hammers  are  provided  with  a  regulating  valve,  which 
enables  one  to  use  a  large  hammer  for  the  lightest  kind  of  chip- 
ping, as  well  as  for  very  heavy  chipping. 

Great  care  should  be  taken  that  the  working  parts  are  kept 
free  from  grit  and  dirt,  and  the  tools  be  kept  well  lubricated 
with  a  good  grade  of  light  oil. 

DRILLS. 

Their  iron  drills  and  wood-boring  machines  are  all  three- 
cylinder  machines.  The  cylinders  oscillate  on  one  valve.  The 
cranks  have  roller  bearings  throughout;  except  the  spindles, 
which  have  ball-bearings.     The  pistons  are  provided  with  roller 


5o8 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  329  —thf.  mo.x.^rch  long-stroke  rivetf.r. 


Q 


a 


■5.  ^r;   £ 


O  13 


if    > 


o  -g  p  > 


C     i- 


M    b« 


H 


Kp^  w^m 


%' 


f»§ 

:,  handle  ; 

plunger 

k'alve-bloi 

i-nut  ;  18, 

IJg-*® 

£ 

M   cj    u    c 
.r?   C    0)    S 

ioff/iialsl 

I,  Handle  tr: 
pin  ;    7,   valve  h. 
block  plug  wash 
coupling-sleeve 

PNEUMATIC    TOOLS.  309 

bearings  where  they  connect  to  the  crank,  which  is  a  solid 
three-point  crank  made  of  tool  steel,  and  hardened  for  the  roller 
bearings.  They  use  cut  gears ;  the  pinions  are  made  of  tool 
steel  and  hardened.  The  wood-boring  machines  are  made  re- 
versible, the  reversing  throttle  and  starting  throttle  being  in 
one  piece  and  also  forming  part  of  the  hose  connection.  The 
Monarch  drill  No.  4,  which  is  a  combination  drill,  and  can  be 
used  for  either  wood-boring  or  iron-drilling,  can  be  made  re- 
versible, by  sliding  a  small  screw  on  the  throttle  valve.     This 


Fig.  331.— monauch  piston  air  drill  no.  i. 

drill  is  especially  desirable  for  expanding  flues  and  for  tapping 
purposes. 

The  No.  I  Monarch  drill  has  a  capacity  for  drilling  and 
reaming  up  to  2^  inches  in  diameter  in  any  kind  of  metal,  and 
is  economical  in  the  consumption  of  air,  only  consuming  about 
20  cubic  feet  of  free  air  per  minute;  it  weighs  but  32  pounds, 
and  runs  about  250  revolutions  per  minute.  It  can  be  used 
within  three  inches  of  a  corner,  and  measures  14  inches  from 
end  of  feed  screw  to  end  of  spindle.  All  the  gears  and  working 
parts  are  well  protected  from  dirt,  and  all  moving  parts  can  be 
oiled  while  machine  is  running. 

The  Monarch  No.  4  drill  is  built  on  the  same  principle  as 
all  of  this  company's  drills,  having  three  cylinders  with  a  solid 


5IO  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

three-way  crank  made  of  tool  steel,  to  which  the  three  pistons 
are  attached,  with  roller  bearings  in  each  crank  connection. 

This  machine  will  drill  a  hole  up  to  i^  inches  in  any  kind 
of  metal;  it  makes  about  375  revolutions  per  minute,  consum- 
ing about  18  cubic  feet  of  free  air  per  minute.  It  weighs  20 
pounds,  and  is  arranged  so  that  it  can  be  made  reversible  by 
simply  pushing  a  small  button  in  or  out  on  the  throttle  valve. 
This  drill  is  especially  desirable  for  stay-bolt  tapping,  reaming. 


Fig.  332.— monarch  drill  no.  4. 

expanding  flues,  and  for  various  other  purposes.  By  taking 
the  feed  screws  off  and  substituting  a  handle  it  can  be  used  as 
a  wood-boring  machine. 

PNEUMATIC    TOOLS    OF    THE    PHILADELPHIA    PNEUMATIC    TOOL 
COMPANY,    PHILADELPHIA,    PA. 

The  pneumatic  hammers  of  this  company  are  made  in  four 
sizes,  of  8,9,  loi,  and  12  pounds  weight,  for  riveting,  chipping, 
and  calking.  They  are  made  on  the  constructive  lines  of  the 
"Little  Giant,"  detailed  on  other  pages  of  this  work.  Air  re- 
quired per  minute  according  to  size,  from  10  to  14  cubic  feet. 

The  pneumatic  hold-on  has  an  air  piston  and  die  which  is 
held  to  the  rivet  with  the  force  of  the  air  pressure  due  to  the 
area  of  the  piston.  The  length  of  the  cylinder  and  die  is  12 
inches,  length  of  stroke  3I  inches. 


PNEUMATIC    TOOLS. 


511 


Chipping  by  the  pneumatic  hammer  and  chisel  is  vastly 
ahead  of  the  power  of  human  muscle  for  effective  work.  Our 
illustration  (Fig.  335)  shows  what  can  be  done  with  a  No.  3 


Fig.  333.— thk  riveting  hammer. 

hammer  and  chisel  in  rolling  up  the  chips  on  a  strip  of  |-inch 
boiler  plate  at  the  rate  of  i  foot  per  minute,  using  air  at  80 
pounds  pressure  per  square  inch. 

Chipping  of  any  kind,  whether  on  wrought  or  cast  iron,  steel, 
or  even  the  softer  metals,  is  a  drag  life  to  the  mechanic,  who 
can  find  relief  from  the  irksome  task  only  by  stopping  the  slow 
and  tedious  work  to  rest  his  wearv  muscles ;    but  when  he  can 


Fig.  334.  -pneumatic  hold-on. 

roll  off  a  big  chip  at  the  rate  of  a  foot  a  minute  by  air  power, 
the  mechanic  art  becomes  a  pleasant  pastime. 

We  illustrate  in  Figs.  336  to  338  the  foundry  air  tools  of 
the  Philadelphia  Pneumatic  Tool  Company  :  the  light  sand  ram- 
mer   operated    by   an   ordinary  pneumatic    hammer,   a   special 


512 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


Fig.  335.— fast  chii'Pi.ng. 

double-handle  rammer,  and  an  adjustable  rammer  for  suspen- 
sion from  a  crane. 

Power  rammers  for  heavy  work  in  foundries  are  compara- 
tively recent  innovations,  and  from  their  simple  construction 
and  the  enormous  amount  of  work  that  they  will  accomplish 
they  are  being  rapidly  adopted  in  this  country  and  in  Europe. 


Fig.  336.— light  rammer. 


Fig.  337.— tvvo-haxdi.e  rammer. 


PNEUMATIC    TOOLS. 


513 


By  the  use  of  these  machines  one  man 
can  readily  do  the  work  of  from  eight  to 
twelve  men.  All  he  has  to  do  is  to  direct 
the  blows  of  the  rammer,  moving  the  ma- 
chine about  over  the  work  by  means  of 
the  handles. 

These  rammers  use  air  at  a  pressure 
of  about  80  pounds  per  square  inch,  and 
strike  from  250  to  300  blows  per  minute. 
The  air  supply  is  absolutely  under  the 
control  of  the  operator,  and  he  can  thus 
regulate  the  force  of  the  blow  to  the 
utmost  nicety,  and  start  and  stop  the  ram- 
mer at  will. 

The  light  pneumatic  rammer  is  simi- 
lar in  construction  to  the  heavier  type  of 
pneumatic  rammers,  but  still  is  light 
enough  to  be  easily  handled  by  the  oper- 
ator. It  is  at  the  same  time  sufficiently 
heavy  for  its  inertia  to  absorb  any  vi- 
bration that  may  arise  from  the  rapid 
reciprocation  of  its  piston  and  rammer 
head.  The  valve  mechanism  and  parts 
are  as  simple  as  is  consistent  with  smooth 
working,  and  are  suitably  enclosed  and 
therefore  free  from  dust  and  dirt.  The 
rammer  head  is  a  hexagon  and  can  be 
turned  at  the  will  of  the  operator.  The 
weight  of  this  tool  is  45  pounds,  and  it 
strikes  250  to  300  blows  per  minute,  with 
an  air  pressure  of  50  to  100  pounds  per 
square  inch,  only  15  cubic  feet  of  free  air 
per  minute  being  used  when  in  contin- 
uous operation.     The  air  is  admitted  to 

the  handle  on  the  right  side,  its  admission 
33 


Fig.    338, 


-SUSPENDED     RAM- 
MER. 


5  14  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

being  controlled  by  a  throttle  lever  under  the  thumb  of  the 
user;  the  exhaust  passes  through  the  handle  on  the  left. 
Speed  and  force  of  the  blow  can  be  varied  at  will.  A  number 
of  different-shaped  heads  are  provided  with  each  machine. 
These  are  attached  to  the  rammer  rod  by  means  of  a  taper  fit, 
and  may  be  changed  in  less  than  half  a  minute  and  without 
letting  go  of  the  handle. 

The  constructive  features  of  the  hammers  and  rammers  of 
this  company  are  based  on  the  Keller  patents. 

THE    COUNTERBALANCED    SAND-RAMMER    IN    FOUNDRY    WORK. 

In  Fig.  338  is  represented  one  of  the  modern  adjuncts  of  a 
foundry  for  the  saving  of  the  severe  labor  of  ramming  large 
moulds.  This  sand-rammer  is  accurately  counterbalanced  and 
weighs  with  its  complete  rig  nearly  300  pounds.  It  is  oper- 
ated by  air  pressure  of  about  40  pounds  per  square  inch,  and 
will  deliver  300  blows  per  minute. 

The  maximum  stroke  is  7  inches,  and  the  intensity  and 
length  of  stroke  may  be  varied  at  the  will  of  the  moulder  by 
simply  altering  the  distance  of  the  rammer  from  the  sand. 

THE    PNEUMATIC    SAND-SIFTER. 

The  meagre  mechanism  of  the  foundry  has  lately  received 
an  important  addition  in  the  machine  illustrated  in  Fig.  339. 
It  is  a  sand-sifting  machine,  operated  by  compressed  air. 
It  consists  of  a  heavy  oak  frame,  containing  a  swinging  rid- 
dle or  sieve,  that  can  be  removed  by  simply  lifting  it  out  of  the 
frame  when  necessary  to  use  a  sieve  of  different  mesh.  The 
motive  power  is  a  substantial  balanced  rotary  motor  of  the  Chi- 
cago Pneumatic  Tool  Company,  which  drives  the  gear  connected 
to  the  three-pointed  knocker  attached  to  the  sieve.  Foundries 
which  are  using  these  machines  state  that  they  not  only  cover 
their  cost  in  a  short  while  by  economy  in  labor,  but  that  the 
tempering  of  the  sand  can  be  done  much  better  than  by  hand. 


PNEUMATIC    TOOLS. 


515 


One  of  the  numerous  special  employments  of  compressed  air 
in  foundry  work  is  the  revolving  steel  brush  for  cleaning  cast- 
ings, operated  by  a  rotary  air  motor.     It  finds  many  places  for 


Fig.  339.— pneumatic  sand-sifter. 

useful  work  where  the  sand  blast  is  not  available,  especially  for 
inside  cleaning  after  cores  and  moulding  sand  have  been  re- 
moved. These,  with  the  many  other  applications  of  special  air- 
driven  tools  noted  in  this  work,  suggest  the  inevitable  conclusion 
that,  when  once  you  have  compressed  air  available,  the  number 


3 


Fig.  340.— pneumatic  casting  cleaner. 


of  convenient  and  economical  possibilities  that  it  presents  to 
the  progressive  operator  is  surprising,  and  its  field  of  service 
broadens  with  amazing  and  gratifying  rapidity. 


516 


COMPRESSED    AIR   AND    ITS   Al'I'LICATIONS. 


THE    MOULDING    MACHINE    IN    THE    FOUNDRY. 

One  of  the  best  labor-savers  in  the  foundry  is  the  pneumatic 
moulding  machine.  The  early  forms  of  small  flask  moulding 
machine  required  shafting,  belts,  and  gears  to  operate  them, 
which  are  not  always  convenient  in  a  foundry  moulding-room. 
The  pneumatic  system  requires  only  a  compressed-air  pipe 
from   the  source  of  compressed-air  supply  in  the  main  works 

with  connections,  when  the 
machine  is  ready  for  work. 
The  machine  is  constructed 
on  the  lines  of  a  hydraulic 
lift,  except  that  the  pressure 
piston  is  operated  by  direct 
air  pressure  of  from  75  to  80 
pounds,  as  used  in  the  oper- 
ation of  other  pneumatic 
machines  and  in  machine 
and  constructive  works. 
The  upper  platen  is  adjusted 
and  fixed  in  its  working  position  by  tie  rods  jointed  at  the  bot- 
tom of  the  machine,  by  which  it  can  be  moved  off  from  over  the 
flask  for  filling  with  sand,  and  removing  patterns  and  flask. 
The  lower  platen  carrying  the  flask  moves  upward  by  the  air 
pressure  in  the  cylinder  and  compresses  the  sand  by  a  weight 
equal  to  several  thousand  pounds,  merely  by  turning  a  three- 
way  cock  as  shown  at  the  right-hand  side  of  the  cut.  After 
ramming,  the  head  is  pushed  back,  and  the  match  and  drag 
are  turned  over  in  the  usual  way.  The  match  is  then  removed 
and  the  cope  flask  is  fitted  over  the  pins ;  parting  and  moulding 
sand  is  then  filled  into  the  cope  and  put  under  pressure.  A 
pneumatic  vibrator,  made  on  the  lines  of  the  vibrating  piston 
in  a  pneumatic  hammer,  is  attached  to  the  flask,  by  which  a 
.sharp  tremor  is  set  up  in  the  vibrating  frame  and  patterns,  when 
the  cope  and  patterns  may  be  drawn  in  the  usual  way. 


Fig.  341.— pneumatic  moulding  machine. 


PNEUMATIC    TOOLS.  517 

The  pneumatic  moulding  machines  are  made  in  several  sizes 
by  the  Tabor  Manufacturing  Company,  Philadelphia,  Pa. 

THE    FLUE-WELDING    HAMMER. 

A  most  important  adjunct  of  the  locomotive  shop.  It  is  used 
for  piecing  out  and  welding  out  tubes  which  have  been  damaged 
by  the  burning  of  end  or  by  removal. 


Fig.  3^2.— the  pneumatic  flue-welding  machine. 
Chicago  Pneumatic  Tool  Company,  Chicago,  111. 

A    PNEUMATIC    ROCK    DRILL    AS    A    HAMMER. 

This  consists  essentially  of  a  drill  mounted  in  a  forged  steel 
frame,  which  is  suspended  by  the  arms  (shown  in  Fig.  343)  to  a 
frame  with  holding  brackets ;  making  a  rig  that  can  be  handled 
with  ease,  and  doing  the  work  required  in  less  time  and  at  a 
lower  cost  than  has  been  done  heretofore  by  hand. 


5l8  COMPRESSED    AIR    AND    ITS   APriJCATIONS. 

It  has  been  used  extensively  in  the  construction  work  on  the 
piers  for  the  new  East  River  Bridge,  for  driving  drift  bolts.     A 
record  of  its  performance  there  has  been  kept,  establishing  there- 
by another  and  permanent  use  for  rock  drills  in  a  new  field. 
Is  is  a  large  type  of  the  pneumatic  hammer.     It  is  the  Little 

Giant    drill    of     the    Rand 
Drill  Company. 


COMPRESSED-AIR  DRILLS  OF 
THE  PHILADELPHIA 
PNEUMATIC  TOOL  COM- 
PANY. 

These  are  of  the  rotary 
type  specified  in  the  gen- 
eral description  on  another 
page,  and  are  made  in  two 
sizes,  weighing  45  and  58 
pounds,  and  using  35  cubic 
feet  of  air  per  minute  for 
full  service.  The  small 
size  will  drill  a  i|-inch  hole 
in  steel,   while  the  larger 

Fig.  343.- pneumatic  drift-bolt  driver. 

size  has  a  capacity  of 
drilling  a  3-inch  hole  in  steel,  with  80  pounds  air  pressure.  It 
is  a  powerful  all-round  machine  for  drilling,  reaming,  tapping, 
and  stay-bolt  screwing.  The  motor  blades  are  fitted  with 
metallic  packing  which  automatically  takes  up  wear  and  main- 
tains efficiency  of  the  working  parts. 

AIR    DRILLS    OF    THE    STOW    FLEXIBLE    SHAFT    CO. 

In  Fig.  345  is  illustrated  the  rotary  motor  drill  made  on  the 
lines  of  the  patent  of  Caid  H.  Peck,  No.  507,752,  consisting  of 
a  rotary  motor  revolving  on  the  drill  spindle  and  reducing  its 
speed  motion  to  the  spindle  through  a  set  of  differential  gears. 


AIR    MOTOR   DRILLS, 


519 


II  , ,  i 


Fig.  C144.— pneumatic  rotary  drill. 


Fig.  345.— air  drills  of  the  stow  flexible  shaft  company,  Philadelphia,  pa. 


520 


COMPRESSED    AIR   AND    ITS   Al'PLICATIONS. 


Air  is  admitted  through  one  handle  by  the  lift  of  the  valve 
lever,  into  the  inside  of  the  piston,  and  is  forced  out  through 
holes  directly  against  the  vanes ;  this  starts  the  piston  to  re- 
volving, and  when  it  gets  around  to  the  other  handle  this  air 
has  done  its  work  and  is  exhausted. 

The  motion  of  the  piston  is  transmitted  through  the  double 
sun-and-planet  gears  in  the  gear  case  to  the  spindle,  and  the 
speed  of  this  spindle  is  regulated  by  the  number  of  gears.  In 
what  is  called  the  single-geared  machine,  as  illustrated  in  the 
right-hand  figure  of  the  cut,  the  speed  is  reduced  to  one  degree, 


Fig.  346.— air  motor  operating  a  drill  with  a  stow  flexible  shaft. 


while  in  the  double-geared    machine  there  is  a  second  set  of 
gears,  and  the  speed  is  only  half  as  great. 

The  air  motor  is  composed  of  a  pair  of  cylinders,  oscillating 
on  centres,  taking  air  from  a  cylindrically  faced  air  chest, 
through  suitable  passages  and  ports,  and  giving  motion  to  the 
crank  shaft.  This  is  the  strong  point  of  the  machine;  it  is 
made  from  the  solid  forged  steel,  and  w^ill  stand  all  the  work 
that  can  be  put  on  it  safely.  The  normal  speed  of  about  1,200 
revolutions  is  reduced  by  a  set  of  speed-reducing  gears  in  the 
case  at  one  end,  and  the  other  end  has  a  small  balance-wheel  and 
a  lever  for  starting  or  for  slowly  working  by  hand  if  necessary. 


AIR    -MUTUR    DRILLS    AND    MOISTS. 


521 


AIR    DRILLS    AND    HOISTS     OF    THE     EMPIRE     ENGINE    AND    MOTOR 
COMPANY,    ORANGEBURG,    NEW    YORK. 

The  drills  of  this  company  are  made  in  five  sizes,  having  a 
capacity  for  drilling  in  metal  from  y\  to  i^-inch  holes.  They 
are  driven  by  a  horizontal  ro- 
tary motor  with  a  pinion  mesh- 
ing into  two  intermediate 
gears,  and  they  into  an  inter- 
nal gear  rack,  which  is  sta- 
tionary, being  held  in  place 
by  the  cylinder  head.  The 
two  intermediate  gears  are 
placed  radially  on  the  arms  of 
the  spindle,  which  travels 
with  the  gears,  thereby  equal- 
izing the  strain  on  bearings 
and  making  friction  light. 

The     air-motor    hoists     of 
this  company  are  illustrated  in 
Figs.  349  and   350.     They  are  operated  by  a  rotary  motor  con- 
taining two  blades  in   an  eccentrically  located  piston  as  shown 


Fig. 347.  — BREAST   DRILL. 


Fig.  348. -the  rotary  movement. 


522 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


PNEUMATIC    HAMMERS. 


523 


in  the  detailed  cut,  and  geared  by  double  pinions  to  large  gear 
wheels  with  differential  chain  sheaves  on  the  main  shaft. 
They  do  not  depend  upon  air  pressure  to  sustain  the  load, 
being  provided  with  a  brake.  They  are  also  made  to  run  on  a 
suspended  trolley  or  boom  of  a  jib  crane. 

PNEUMATIC  TOOLS  OF  THE  C.  H.  SHAW  PNEUMATIC  TOOL 
COMPANY,  DENVER,  COLO. 

The  tools  are  very  simple  in  their  construction,  yet  efficient 
for  work.      The  chipping  and  calking  hammer  is  made  up  of  six 


Fig.    351.— IHIi   ECLIPSE   HAMMER. 

pieces  and  is  so  simple  in  form  that  any  machinist  can  renew 
the  parts  liable  to  wear.  It  has  a  spring  handle  and  is  valve- 
less  in  the  operating  parts,  the  admission  air  valve  being  oper- 
ated by  the  grasp  of  the  handle. 

The  marble-cutter's  hammer  is  equally  simple  in  construc- 
tion ;  it  has  a  compression  air  valve  operated  by  the  pressure  of 


Fig.  352.— parts  of  the  eclipse  hammer. 


524 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


the  thumb,  and  also  a  screw  regulating  valve  to  regulate  the 
air  pressure  for  very  light  work.  Usual  air  pressure,  30  to  50 
pounds  for  marble  work. 

The  two-cylinder  compound  air  drill  of  this  company  is  illus- 
trated in    Fig.    354.       The    arrangement    of    the    pistons    and 


Fig.  353  —the  marble  cutter's  hammer. 

connections  is  such  as  to  allow  of  no  dead  centre,  and  the  com- 
pounding of  the  cylinders  carries  the  exhaust  nearly  to  atmos- 
pheric pressure.  A  more  powerful  drill,  having  four  cylinders, 
is  manufactured  by  the  same  firm.  This  company  also  makes  a 
single-cylinder  rotary  drill  or  tapping  machine  with  a  four- 
bladed  piston  having  no  dead  centre  or  weak  place  in  its  revo- 


FlG.    354.— COMPOUND  AIR  DRILL. 


PNEUMATIC    HAMMERS. 


525 


lution.  It  is  made  in  two  sizes,  for  drilling  and  tapping,  up  to 
i|-and  i^-inch  holes  respectively,  and  is  very  suitable  for  boiler 
work. 

PNEUMATIC  TOOLS  OF  THE  AMERICAN  PNEUMATIC  TOOL 
COMPANY,  NEW  YORK  CITY. 

The  tools  of  this  company  have  been  long  in  use  for  metal 
and  stone  work,  and  are  simple  in  design  and  effective  in  their 


Fig,  355.— pneumatic  hammers  of  the  American  pneumatic  tooi,  company. 


working  power.     They  are  made  in  three  sizes,  for  light,  me- 
dium, and  heavy  work. 

The  details  of  the  parts  of  these  hammers  are  as  follows : 
the  handle  and  valve-seat  case  screwed  upon  the  cylinder,  the 
valve  block  or  seat  containing  the  air  passages,  and  the  valve 
spool  which  operates  automatically  in  the  valve  block,  the  pis- 
ton, and  tool  bushing. 


526 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


The  stone-dressing  pneumatic  tools  of  this  Company  are 
here  illustrated  in  four  sizes,  of  which  the  A  size  is  a  very  light 
tool  for  tracing  and  small  lettering;  the  BX  size  is  for  heavy 
lettering  and  carving,  and  the  other  two  are  for  heavier  cutting 
and  roughing. 

The  lighter  tools  are  for  lettering  and  finishing.  In  this 
class  the  piston  contains  the  automatic  valve,  and  part  of  the 


Fig.  356— stone-dressing  pneumatic  hammers. 

exhaust  opens  at  the  nose  of  the  tool  to  blow  away  the  chips 
and  dust. 

The  detailed  parts  are  shown  in  Fig.  357.  i  is  the  cylinder 
screwed  to  the  nose-piece  7,  and  covered  by  a  jacket  4.  The 
piston  5  is  perforated  across  the  centre  and  contains  the  spool 
valve  and  internal  ports  and  air  passages  for  operating  the  pis- 
ton, their  counterpart  being  through  the  walls  of  the  cylinder, 
communicating  with  the  inlet  and  exhaust  passage  shown  under 
the  jacket.  The  throttle  sleeve,  3,  regulates  the  air  flow  by 
controlling  the  exhaust;    6  is  a  bumper  washer,  fixed  by  the 


PNEUMATIC    TOOLS. 


527 


528 


COMPRESSED    AIR   AND    ITS    APPLICATIONS, 


shoulders  of  the  cylinder  and  nose-piece.  The  tool-holder  is 
held  back  aw'ainst  the  washer  by  a  helical  spring,  15;  1 1  is  a 
U-shaped  wire  to  keep  the  throttle  nut  2  from  turning;  12  is  a 
helical  spring  to  keep  the  throttle  sleeve  to  its  conical  bearing; 
14  is  a  spline  shown  at  the  top  of  the  piston  and  fixed  in  the  cyl- 
inder to  keep  the  piston  from  revolving  and  displacing  the  air 
ports.  This  company  also  makes  a  valveless  stone  hammer 
equal  to  all  the  requirements  of  light  stone-cutting  and  letter- 
ing, and  containing  but  few  working  parts  in  its  construc- 
tion. 

The  pneumatic  stone-dressing  machine  (Fig.  358)  is  one  of 
the  most  convenient  and  best  labor-saving  appliances  used  in  a 
stone-cutting  establishment.  A  hammer  of  the  larger  dimen- 
sion, mounted  on  the  end  of  a  traveller  running  freely  between 
rollers,  suspended  and  balanced  on  a  post  resting  on  a  truck,  is 
a  rig  that  gives  complete  control  of  the  motion  of  the  tool  over 
the  face  of  a  block  of  stone.     The  hand  easily  guides  the  tool 


Fig.  359.— little  gl\nt  air  drill. 


for  evening  the  surface  and  for  hammer  dressing,  a  most  tedi- 
ous operation  when  done  by  hand.  The  exhaust  is  at  the 
top  of   the  tool  cylinder  and  is  directed  toward  the  cutter  by 


PNEUMATIC   TOOLS.  529 

a  hose,  thereby  keeping  the  face  of  the  stone  clear  of  chips  and 
dust  for  the  inspection  of  the  workman. 

AIR   TOOLS    OF   THE    STANDARD    PNEUMATIC    TOOL   COMPANY, 

CHICAGO,   ILL. 

We  illustrate  in  figs.  359  and  360  the  "  Little  Giant"  revers- 
ible piston  type  air  motors,  used  for  all  kinds  of  portable  drill- 
ing, reaming,  and  tapping  in  the  machine  shop  and  in  outdoor 


Fig.  :!6o.— small  two-piston  motor  drill. 

practice.  The  motor  consists  of  four  single-acting  cylinders,  in 
pairs,  connected  to  opposite  ends  of  a  double  crank  shaft,  so  that 
the  shaft  receives  four  impulses  at  each  revolution,  and  develops 
from  i^  to  3!  horse  power,  in  the  various  sizes,  at  80  pounds  air 
pressure. 

This  company  also  makes  the  "  Little  Giant "  pneumatic 
hammers,  air  hoists,  motor  chain  hoists,  air  car-jacks,  stay-bolt 
nippers,  and  yoke  riveters. 

COMPRESSED-AIR    RIVETERS. 

Direct-pressure  riveters  are  used  as  stationary  machines  for 
riveting  boiler  and  tank  shells.  Their  large  pistons  act  directly 
upon  the  rivet,  and  they  are  quick-moving  powers  for  this  work. 
The  toggle-joint  movement  with  small  piston  and  cylinder 
mounted  on  a  portable  frame  has  become  the  general  type  for 
structural  work.  The  Allen  yoke  riveter  is  one  of  the  types  in 
which  the  toggle  joint  is  pivoted  to  a  cam  bar  and  also  within 
34 


530 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


the  trunk  piston.  By  the  differential  or  trunk  form  of  piston 
the  return  stroke  economizes  the  compressed  air,  while  the 
large  piston  area  gives  great  power  to  the  riveting  stroke. 

A  double-lever  riveter  is  sketched  in  Fig.  362,  in  which  the 
air  piston  acts  directly  upon  the  toggle  joint  by  drawing  it  to- 
ward the  cylinder.     It  is  balanced  on  a  yoke. 

These  sketches  are  from  the  early  models  of  the  Allen  pat- 
ents. These  riveters  have  been  in  practical  operation  for  many 
years  as  standard  pneumatic  tools.     They  have  been  remodeled 


Fig.    361.— ALLEN   MODEL. 


Fig.  362.— double  lever  riveter. 


and  improved  to  meet  the  requirements  of  all  kinds  of  struc- 
tural work,  until  there  seems  to  be  no  place  that  a  pneumatic 
riveter  cannot  reach,  as  shown  by  accompanying  illustrations. 


PNEUMATIC     RIVETERS     OF     THE     CHESTER     B.     ALBREE 
IRON    WORKS,    ALLEGHENY,    PA. 

The  riveters  of  this  company  are  of  the  toggle-joint  type, 
giving  the  theoretically  correct  pressure  due  to  the  increasing 
resistance  of  the  rivet  during  the  driving  stroke.  A  connecting 
bar  holds  the  thrust  member  of  the  rolling  toggle  to  prevent 
binding  of  the  rivet  piston,  which  is  drawn  back  by  a  helical 
spring.  A  screw  on  the  riveting  die  serves  for  adjustment  of 
throw.  A  special  design  is  shown  in  Fig.  363  for  riveting  col- 
umns, as  the  horn  can  be  inserted  between  the  channels  and 
braces.  Fig.  365  shows  how  easily  the  riveter  may  be  inverted 
with  the  aid  of  the  universal  bail. 


PNEUMATIC    RIVETERS. 


531 


532 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


AIR    HOISTS. 


The  application  of  air  hoists  to  cranes,  over-lathes,  planers, 
drilling  machines,  and,  in  fact,  to  all  conditions  in  which  a  hoist 
may  be  useful,  is  now  made  in  an  almost  endless  variety  of 
ways  to  meet  the  requirements  of  machine  shop  and  foundry 


Fig.  365  —inverted  u.\  um\kksai.  bail. 


practice.  The  most  common  type  is  the  simple  cylinder  hoist, 
either  vertical  or  horizontal,  or  in  combination  with  an  inter- 
mediate inelastic  fluid,  water  or  oil. 

In  many  instances  direct-acting  hoists  may  be  readily  ap- 
plied to  hand-power  cranes  already  in  use,  in  which  the  hoist 
may  be  hooked  to  the  gear  tackle  for  adjusting  the  height,  when 
the  air  hoist  may  be  used  for  quick  work. 


PNEUMATIC    HOISTS. 


533 


==% 


Fig    366 —safety 
stop  air  hoist. 


In  Fig.  366  is  shown  the  safety  stop  applied  to  the  direct 
hoist  for  arresting  the  lift  automatically  at  any  desired  point  by 
closing  the  air  valve,  the  lift  being  otherwise 
controlled  by  the  three-way  cock  and  double 
lanyard. 

THE     OIL-GOVERNED     PNEUMATIC     HOIST     OF 

THE    CRAIG    RIDGWAV    &    SON    COMPANY, 

COATESVILLE,    PA. 

The  top  head  is  enlarged  to  form  a  reservoir. 
To  this  head  is  secured  a  bar  which  has  a  pas- 
sageway through  it  connecting 
with  the  reservoir.  This  fixed 
bar  passes  through  the  piston 
and  enters  the  hollow  piston 
rod.  A  leather  cup  supplemented  by  any 
ordinary  packing-box  makes  a  tight  working- 
joint  at  the  piston  with  the  fixed  bar.  In  the 
reservoir  are  two  valves,  one  a  swing  check 
valve  and  the  other  a  simple  regulating  valve 
with  a  screw  stem.  The  stem  extends  out- 
side the  reservoir  and  is  provided  with  a 
sprocket  wheel  for  regulation. 

The  action  of  the  governing  device  is  as 
follows:  The  piston  is  pulled  down  to  the  end 
of  its  stroke  and  ordinary  machine  oil  is  poured 
into  the  reservoir.  It  passes  the  valves  and 
fills  the  hollow  piston  rod.  If  now  full  press- 
ure of  air  be  under  the  piston  and  the  valves 
be  closed,  the  hoist  cannot  move,  its  move- 
ment being  resisted  by  the  fixed  bar  and  the 
oil  in  the  hollow  rod.  If  now  the  regulating 
valve  be  opened,  the  oil  will  escape  into  the  reservoir,  and  the 
hoist  will  rise  just  as  fast  as  the  oil  can  pass  this  valve,  and  no 
faster.     It  makes  no  difference  how  the  air  is  admitted  to  the 


. 


Fig.    367.  —  oil-gov- 
erned HOIST. 


534 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


hoist,  or  whether  the  hoist  is  loaded  or  empty,  its  motion  is 
controlled  entirely  by  the  oil.  When  the  piston  lowers,  the  oil 
passes  back  into  the  rod  by  the  check  valve. 

An  air  inlet  valve  is  also  connected  with  the  upper  and  the 
under  side  of  the  piston.  The  under  side  of  the  piston  is  always 
connected  to  the  compressor  and  always  under  pressure;  the 
oil  pan  is  also  always  under  pressure.  The  valve  admits  air  to 
and  exhausts  from  the  upper  side  of  the  piston.  No  air  is  con- 
sumed in  lifting  the  load,  the  air  being  used  to  press  the  piston 
down  the  cylinder.     The  air  being  admitted  above  the  piston, 


Fig.  368.— travellixg  crane  and  air  hoist. 

pressure  is  equalized  on  both  sides  and  the  piston  is  forced 
down  the  cylinder  with  a  force  equal  to  the  diameter  of  the  pis- 
ton rod.  The  oil  is  forced  into  the  rod  by  pressure.  Gravity 
is  not  depended  upon  to  lower  the  piston,  and  packings  can  be 
made  and  kept  tight.  No  air  from  the  shop  ever  enters  the 
cylinder  to  carry  in  dirt  and  dust.  All  motions  being  under 
perfect  control,  and  all  done  by  pressure,  jerkiness  and  danger 
are  entirely  overcome.  The  air  pressure,  being  always  under 
the  piston,  is  like  a  big  perfect  spring;  and  with  the  oil  to  reg- 
ulate its  upward  motion,  the  Ridgway  hoist  reaches  a  high  point 
of  perfection. 


PNEUMATIC   HOISTS. 


535 


TRAVELLING   CRANE    WITH    AIR    HOIST. 


The  Ridgway  air  hoists  are  mounted  in  many  ways  to  suit 
the  wants  of  foundries  and  machine  shops.  The  most  common 
plan  is  to  carry  them  upon  travelling  bridges,  swing  cranes,  or 
runways.  The  cut  shows  a  ten-ton  hoist  upon 
a  traveller.  The  cylinder  is  hung  in  a  gimbal 
truck,  and  is  moved  back  and  forth  on  the 
bridge  by  a  pendant  hand  chain.  The  bridge 
is  travelled  by  an  air  engine,  operated  by  cords 
from  the  floor,  or  it  may  be  arranged  to  move 
by  hand.  The  crane  is  connected  to  the  air 
supply  at  end  of  the  runway  by  a  hose.  The 
hose  is  carried  in  sections  by  small  trucks  trav- 
elling upon  one  of  the  tracks  of  the  runway. 
A  better  plan  is  to  carry  the  hose  by  trucks  or 
slides  upon  a  special  track  over  the  centre  of 
the  span.  Slides  are  preferred  by  some  to 
trucks,  in  that  the}'  never  get  out  of  order  or 
need  attention.  As  the  crane  travels  in  one 
direction  the  hose  stretches  out  one  loop  after 
another.  As  it  moves  in  the  opposite  direction 
the  trucks  or  slides  are  pushed  ahead  and 
gather  up  the  hose. 

In  the  smaller  travelling  crane  of  two-ton 
capacity,  the  hoist  is  carried  b}'-  a  trolley  run- 
ning upon  the  lower  flange  of  a  single  I  beam. 
In  this  case  the  hose  is  wrapped  upon  a  reel, 
the  air  being  taken  in  through  the  hollow  axis 
of  the  reel.  The  reel  is  placed  so  the  cylinder 
can  move  past  it  and  cover  the  full  span  of  the  bridge.  The 
hose  is  attached  to  the  air  supply  at  one  end  of  the  runway.  A 
cord  is  run  from  the  reel  to  the  opposite  end  of  the  runway. 
The  pull  of  the  hose  unwinds  it  from  the  reel  as  the  crane 


Fig.  369.  -air  hoist. 


536 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


moves  in  one  direction,  while  the  pull  of  the  cord  winds  up  the 
hose  as  the  crane  moves  in  the  opposite  direction. 

The  festoon  and  the  reel  plan  are  the  two  most  approved 
ways  of  taking  care  of  the  hose.     When  it  can  be  used  the  fes- 
toon plan  will  be  found, 
on  the  whole,  the  cheap- 
est and  best  of  the  two. 


Fig.  370.— self-closixg  valvk. 


AIR  HOISTS  OF  THE  CUR- 
TIS MANUFACTURING 
COMPANY. 

The  air  hoists  of  this 
company  are  made  in 
eleven  sizes,  from  3  to 
16  inches  in  diameter; 
and  with  standard  lifts 
of  4  feet,  or  of  special 
lengths  when  desired. 
These  hoists  have  a 
special  self-closing  valve 
device,  shown  in  the  en- 
larged view  (Fig.370),by 
which  a  helical  spring, 
attached  by  suspender 
chains  to  each  arm  of  the 
valve,  brings  the  valve 
to  its  closure  independ- 
ently of  the  operating  of 
the  hand  chains. 

An  adjustable  stop 
operated  by  a  set  collar 
on  the  piston  rod  stops 
the  load  at  any  set  point, 
by  moving  a  rack  and 
pinion. 


PNEUMATIC    HOISTS. 


537 


538 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


It  has  also  an  adjustment  for  regulating  the  speed  of  the 
hoist  independently  of  the  valve  movement. 


Fig.  372.— loading. 


THE   AIR-HOIST    TRAVELLER    FOR    STORES    AND    WAREHOUSES. 

For  transferring  goods  in  a  ware- 
house or  factory,  or  for  loading  and 
unloading  goods  from  trucks,  nothing 
else  has  been  devised  that  is  so  con- 
venient and  cheap  as  the  air  hoist. 
The  same  power  that  operates  the  ele- 
vators will  compress  sufficient  air  for 
the  operation  of  these  handy  devices. 
The  overhead  trolley  rail  is  readily  in- 
stalled and  can  be  extended  across  the 
street  or  across  alleyways  between  fac- 
tories, to  facilitate  the  dropping  or 
picking  up  of  merchandise  or  machin- 
ery directly  to  or  from  the  trucks.  A 
boy,  with  this  aid,  can  lift  and  convey  loads  that  would  otherwise 
require  a  gang  of  men.  In  Fig.  373  is  shown  a  horizontal  air 
lift  installed  on  an  overhead 
trolley  rail,  for  shops  or  stores 
where  the  ceiling  is  too  low 
to  accommodate  a  vertical 
lift.  With  long  trolley  rails 
winding  among  the  machin- 
ery of  a  factory,  the  air  pipes  may  be  laid 
around  the  works  with  outlets  and  hose  at  con- 
venient places,  which  may  be  uncoupled  when 
the  load  is  lifted  for  long-distance  runs. 

In  Fig.  374  is  shown  the  arrangement  of 
the  overhead  trolley  track,  trolley,  and  sheaves 
for  holding  the  hose  as  it  is  run  out  from  the 
reel  or  hose  drum .     An  arm  on  the  trolley  truck      pig  373._hoisting. 


PNEUMATIC    HOISTS. 


539 


allows  the  hose  to  pass  over  the  sheaves  and  be  drawn  forward, 
or  to  be  pulled  back  by  the  hose  drum,  which  has  sufficient 
tension  to  keep  the  hose  from  dropping  into  inconvenient  loops. 


Fig.  374.— the  overhead  trolley  and  hosi'.  sheaves. 

The  drum  reel  (Fig.  375)  is  counterbalanced  by  a  weight 
and  rope  wound  upon  a  smaller  drum  on  the  same  shaft.  A 
sprocket  and  chain  drives  a  guide  screw  carrying  a  nut,  frame, 
and  sheaves  to  guide  the  winding  of  the  hose  in  its  proper  place 


Fig.  375.— the  hose  drum  and  guide  screw. 


540 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


on  the  reel.  The  end  of  the  hose  is  connected  with  the  hollow 
shaft,  from  the  end  of  which  a  stuflfing-box  allows  the  hollow 
shaft  to  turn  freely  in  a  fitting  connected  to  the  air-pipe  line 
from  the  air-compressor  receiver. 

The  above  illustrated  goods  hoist  and  conveyor  is  in  opera- 
tion at  the  Xason  j\Ianufacturing  Company,  New  York  City. 
Patent  of  Carleton  W.  Nason. 


THE  PNEUMATIC    HOIST    IN    THE    FOUNDRY. AIR    HOIST    OF    THE 

CHICAGO    PNEUMATIC    TOOL    COMPANY. 

In  no.  other  operation  in  the  foundry,  save  the  air  blast,  is 
air  used  to  such  advantage  as  in  air  hoists  and  cranes;   and  not 

least  in  the  sand  rammer.  By 
using  direct-acting  air  hoists 
suspended  from  trolley  tracks, 
swinging,  and  travelling 
cranes,  a  vast  amount  of  heavy 
labor  is  saved.  vSaving  is  the 
measure  of  our  living  in  these 
competitive  times. 

With  overhead  trolley  rails 
and  air  hoists  with  detachable 
hose  couplings,  castings  can  be 
readil}'  conveyed  to  any  part  of 
the  foundry,  or  outside  of  the 
building  to  the  machine  shop. 
Few  realize  how  cheap  an 
air  hoist  is  to  operate,  apart 
from  its  convenience  and  speed  in  handling  loads.  It  has  been 
estimated  that  compressed  air  at  90  pounds  pressure  costs  about 
5  cents  per  1,000  cubic  feet  of  free  air,  or  143  cubic  feet  of 
capacity  in  the  air  lift. 


Fig.    376.— piling   and    siori.ng  c.^st-irun 

COLU.MNS. 


PNEUMATIC    HOISTS. 


541 


Fig.  377.— air  lift,  style  3. 
With  releasing  valve. 


Fig    378.— air  lift,  style  6. 
Diameter,  3  to  6  inches. 


542 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


COMPRESSED-AIR   APPLIANCES    OF    THE    PEDRICK    &    AVER 
COMPANY,    PHILADELPHIA,    PA. 

The  pneumatic  lifts  of  this  company  are  made  with  seamless 
hard  brass  tubing,  with  heads  bolted  through,  and  in  three 
styles,  viz. : 

No.  I  style  has  only  one  valve  for  admitting  and  releasing 
air.     With  this  valve,  the  instant  the  hand  releases  the  operat- 


FlG.  379.— NO.  4  STYLE  ON  TRAVELLING  CRANE. 

3  to  16  inch  cj-linders,  with  anj'  desired  valve  and  controlling  appliance. 

ing  chain  (either  when  raising  or  lowering  the  load)  the  valve 
is  automatically  closed  by  the  air  pressure,  thus  shutting  off  the 
admission  or  discharge  of  the  air  and  stopping  the  load  at  that 
point. 

No.  2  style  is  fitted  with  two  valves.  One  valve  is  for  ad- 
mitting and  releasing  the  air  in  the  cylinder  and  is  left  open  to 
the  supply  when  lifting  the  load.     The  second  valve  is  con- 


FlG.   380.— THE  HORIZONTAL  HOIST. 

With  sheaves  for  draw  hoist,  2  to  i,  for  travelling  cranes  and  boom  hoists. 


PNEUMATIC    HOISTS. 


543 


trolled  by  a  loose  collar  with  a  set  screw,  on  the  piston  rod, 
which  is  adjusted  for  the  height  of  the  lift  desired.  When  the 
load  is  lifted  to  this  height  this  second  valve  automatically 
closes,  cutting  off  the  supply  of  air;  then,  in  case  of  leakage 
from  any  cause,  it  automatically  admits  just  enough  air  to  keep 
up  the  supply  and  retain  the  position  of  the  load. 

No.  3  style  has  three  valves,  the  first  two  valves  being 
identical  with  those  of  the  No.  2  style,  and  with  all  their  ad- 
vantages, while  the  third  valve  is  called  a  releasing  valve  and 


Fig.  3S1.— Horizont.\l  multiple  hoist 
On  a  free  running  trolley  for  cranes  and  booms. 

sustains  the  load  perfectly  stationary  when  it  varies  in  weight 
while  suspended,  as  pouring  out  molten  metal,  etc.  This  is 
obtained  by  the  automatic  action  of  these  valves  releasing  or 
admitting  air  into  the  hoist  cylinder  as  is  necessary  to  keep  the 
load  in  the  same  position. 

AiR-LiFT  Work. 


Amount 

Amount 

of  free  air 

of  free  air 

Diam- 
eter. 

Capacity. 

Lift. 

consumed  per 

4  foot  lift 

at  80  pounds 

pressure. 

Diam- 
eter. 

Capacity. 

Lift. 

consumed  per 

4  foot  lift 

at  80  pounds 

pressure. 

Inches. 

Pounds. 

Feet. 

Cubic  feet. 

Inches. 

Pounds. 

Feet. 

Cubic  feet. 

3 

470 

4 

1. 17 

9 

4.440 

4 

10.88 

4 

930 

4 

2.13 

10 

5.630 

4 

13-50 

5 

1,400 

4 

3-31 

12 

8,015 

4 

19.58 

6 

1.925 

4 

4.83 

14 

10,803 

4 

26.51 

7 

2,660 

4 

6.63 

16 

14,123 

4 

34-49 

8 

3,660 

4 

8.67 

544 


COMPRESSED    AIR    AND    ITS    AI'l'LICATIONS. 


The  style  shown  in  Fig.  379  is  for  use  in  foundries  or  in 
connection  with  sheave  attachments,  where  the  slightest  move- 
ment of  the  hoist  while  suspending  the  load  is  undesirable. 
This  is  prevented  by  a  specially  arranged  valve  by  which  air  is 
constantly  on  both  sides  of  the  piston,  preventing  jumping  of 
the  piston  and  giving  a  slow,  steady  movement  in  lowering  or 
raising,  and  yet  admitting  of  a  quick  movement  when  necessary. 


THE     DIRECT-ACTING      PNEU- 
MATIC-CHAIN  JIB    CRANE. 

Admitting  compressed 
air  on  the  top  of  the  piston 
by  a  valve  on  the  back  of 
the  mast,  it  is  forced  down- 
ward and  pulls  with  it  the 
piston  rod  to  which  is  at- 
tached a  chain  running  over 
a  sheave  under  the  top  pin- 
tle and  out  to  the  end  of 
the  jib  which  lifts  the  load. 
By  releasing  the  air  on  top 
of  the  piston  the  counter- 
balance on  end  of  chain 
falls,  lifting  piston  into  po- 
sition ready  to  lift  next  load. 
Sheave  wheels  and  top  pin- 
tle of  mast  are  furnished 
with  roller  bearings,  bottom 
pintle  of  mast  having  ball- 
and-socket  bearing.  The 
height  of  lift  is  limited  only 
by  the  head  room ;  and 
where  conditions  are  such 
that  the  load  does  not  have 


Fig.  382.  — DiREcr- acting  pneumatic  crane. 


PNEUMATIC    PUNCH. 


545 


to  be  moved  along  the  jib,  this  style  of  crane  is  particularly 
desirable  on  account  of  its  simplicity. 

In  Fig.  383  is  shown  a  section  of  the  Pedrick  &  Ayer  oil- 


pneumatic  riveter,  in  which  by  the  use  of  differential  pistons  the 
elastic  compression  of  air  at  moderate  pressure  controls  a  small 
piston  acting  upon  an  inelastic  fluid  (oil)  for  generating  a  high 
pressure  upon  the  dolly-bar  or  riveting  piston.     Referring  to 


35 


546 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


the  sectional  cut,  the  movement  of  the  lever  15  operates  the 
cylindrical  three-way  valve  12,  for  driving  the  piston  of  the  air 
cylinder  and  its  plunger  18,  which  passes  through  a  stuffing 
box  44  into  the  oil  chamber,  producing  a  pressure  equal  to  the 
differential  areas  of  the  air  piston  39,  plunger  18,  and  the  dolly- 
bar  piston  13.  In  this  way  a  comparatively  small  air  cylinder 
at  80  pounds  air  pressure  may  be  made  to  exert  a  pressure  of 


Fig.  384.— the  lattice  or  column  kiveter. 

from  10  to  15  tons  on  a  rivet  head.  A  free  floating  piston,  23, 
in  a  small  separate  cylinder,  is  made  by  air  pressure  to  follow 
up  the  oil  charge  in  the  oil  chamber  as  the  dolly  moves  down 
to  the  rivet,  and  allows  the  oil  to  be  drawn  back  by  the  return 
of  the  oil  plunger  and  through  the  air  pressure  on  the  push- 
back  piston  on  the  dolly-bar  28.  A  rear-end  view  is  also  shown 
at  the  left,  indicating  the  position  of  the  oil  cylinder  with  its 


PNEUMATIC    PUNCH. 


547 


floating  piston.  In  charging  the  riveter  with  oil,  the  floating 
piston  is  drawn  to  the  back  end  of  the  cylinder  by  removing 
the  plug  35  and  inserting  the  pull  rod  48. 


COMPRESSED-AIR    PUNCH. 

In  Fig.  385  is  illustrated  a  simple  and  compact  air  punch; 
a  most  convenient  and  easily  handled  punch  for  sheet  and  plate 
work.  It  is  made  by  the  F.  F.  Slocomb  Company,  Wilming- 
ton, Del.,  and  consists  of 
a  hollow  piston  adapted 
to  contain  oil  and  fitted 
with  a  prolongation  or 
tail  rod,  within  which 
tail  rod  a  stationary  tube 
seated  in  the  hook  is 
adapted  to  telescope  ;  the 
oil  being  thereby  forced 
into  and  through  the 
stationary  tube  and 
thence  upon  the  plunger 
into  the  vertical  cham- 
ber of  the  hook,  where 
it  exerts  accumulated 
pressure.  The  air  that 
drives  the  piston  during  the  stroke  is  utilized  to  drive  it  back 
for  another,  being  finally  expelled  through  the  exhaust  during 
the  next  succeeding  stroke.  This  effects  an  important  saving 
in  the  quantity  of  air  used. 

The  cylinder,  cap,  and  hollow  piston  are  made  of  aluminum 
in  order  to  make  the  machine  as  light  as  possible.  It  is  a  great 
saver  in  time  and  help  in  sheet  metal,  plate,  and  light  struc- 
tural work. 

The  smallest  size,  No.  o,  punches  y^-inch  metal  and  under, 
and  weighs  but  28  pounds,  using -j%  cubic  foot  free  air  per  stroke. 


Fig.    385. -CASEY   PNEUMATIC   PUNCH. 


548  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

No.  I  punches  up  to  f-inch  metal,  weighs  143  pounds,  and  uses 
I  cubic  foot  free  air  per  stroke.  No.  2  punches  f-inch  metal, 
weighs  775  pounds,  and  uses  3  cubic  feet  free  air  per  stroke. 
No.  3  is  a  still  larger  machine  adapted  for  heavy  punching, 
using  5  cubic  feet  free  air  per  stroke. 


COMPRESSED    AIR    IN    RAILROAD    SHOPS. 

There  seems  to  be  no  end  to  the  use  of  compressed  air 
in  railroad-car  construction  and  repair  shops.  Besides  driv- 
ing motors  for  drilling,  reaming,  and  wood-boring;  hammers 
for  chipping,  riveting;  motors  for  running  special  machines; 
lifts,  jacks,  and  many  other  devices  described  in  this  work,  we 
may  add  a  pneumatic  press  for  bending  eye-bolts,  brake-hanger 
hooks,  bar-straps  for  braces,  and  truck-frame  construction. 
The  horizontal  pneumatic  press,  called  the  bulldozer,  mounted 
on  a  strong  frame  with  abutting  anvils,  with  the  frame  on  wheels 
for  portability,  is  a  handy  helper  for  the  power  to  easily  ac- 
complish a  great  variety  of  work  in  the  car  shop.  It  is  a  won- 
derful blacksmith  helper  in  bending,  upsetting,  and  riveting  on 
the  parts  of  locomotive  and  car  work,  upon  which  a  large  num- 
ber of  processes  are  necessarily  duplicated.  The  stationary 
pneumatic  hammer  in  the  blacksmith  shop  is  a  most  useful  ap- 
pliance, and  does  away  with  the  discomforts  of  the  steam  ham- 
mer by  giving  fresh,  cool  air  to  the  workers.  Pneumatic 
punches  and  shears  are  among  the  useful  tools  not  here  illus- 
trated. The  portable  sand -papering  disc  and  the  emery  wheel 
are  now  driven  by  a  rotar)'  air  motor. 

The  stay-bolt  cutter  operated  by  the  direct  pressure  of  air  is 
one  of  the  handy  tools  in  the  boiler  shop.  The  shearing  off  of 
stay  bolts  is  tedious  work  when  done  by  hand.  A  balanced 
stay-bolt  cutter  or  shears  operated  by  direct-air  pressure  and 
the  double  toggle  joint  and  lever,  as  shown  in  Fig.  386,  has  an 
immense  power  for  cutting  and  shearing.  Thus  a  cylinder  only 
10  inches  in  diameter  at  60  pounds  air  pressure  gives  a  gross 


PNEUMATIC    TOOLS. 


549 


pressure  to  the  toggle  and  levers  of  4,700  pounds;  which  mul- 
tiplied by  a  leverage  of  3  is  equal  to  7  tons ;  which  again  in- 
creased by  the  size  of  the  angle  of  the  toggles  may  be  made 
to  apply  a  pressure  of  40  or  more  tons 
to  the  biting  jaws,  accomplishing  work 
in  a  few  seconds  that  would  otherwise 
require  several  minutes.  This  gain 
counts  in  the  day's  or  week's  work,  and 
soon  pays  in  every  department  for  a 
complete  equipment  in  compressed-air 
appliances. 

One  of  the  many  useful  tools  oper- 
ated by  compressed  air  in  the  locomo- 
tive-boiler shop  is  the  bolt-nipper,  of 
which  one  type  of  air-operated  nippers 
has  cut  off  in  one  case  all  the  stays  in  the  firebox  of  a  Brooks 
"  ten-wheeler  "  in  three  hours,  and  was  handled  by  two  boys,  a 
job  which  formerly  occupied  a  boilermaker  and  helper  nearly 
two  days.  This  is  a  saving  in  cost  of  about  90  per  cent,  and 
the  same  work  with  this  tool  in  another  erecting  shop  resulted 
in  a  saving  of  86  per  cent.  The  nippers  cutting  off  from  both 
sides  at  once,  do  not  injure  the  sheet  or  loosen  the  thread,  as 
may  be  done  by  chipping  the  stays  off. 


Fig.  386.— stay-bolt  cutters. 


Fig.   3S7.-THE   PXEUM.\TIC  Sl'AY-BOI.T   BITEU. 

Two  strong  pivoted  levers  operated  by  an  air  piston.     No.  i  will  cut  stay- 
bolts  up  to  I  inch  diameter,  and  No.  2,  up  to  1%  inch  diameter. 


550 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


Figs.  388  and  389  are  a  front  view  and  side  section  of  a  car- 
wheel  jack,  used  for  loading  fitted-up  car-wheels  upon  platform 
cars  for  transportation.  Fitted  to  the  head  of  the  pneumatic 
piston  is  an  arm  with  bearings  which  engage  the  axles  and  lift 
them  to  the  level  of  the  platform  car  upon  which  they  are  to  be 


Fig.  388— PiNi.u.MAiic  car-wheel  jack. 


Fig.  389.— sec  I  ion   of   car-wheel 

JACK. 


loaded.  By  this  device  the  man}^  accidents  to  laborers  loading 
in  the  old  way  by  skids  are  entirely  eliminated. 

The  jack  is  usually  a  cast-iron  cylinder  sunk  in  a  pit  be- 
tween the  rails  of  the  track  on  which  the  wheels  are  to  be 
loaded. 

Apart  from  the  many  pneumatic  tools  used  in  railroad 
shops  described  and  illustrated  in  other  parts  of  this  book,  we 
may  mention  the  pneumo-hydraulic  rail-bender  and  straight- 
ener,  the  pneumatic  machine  for  putting  on  air-brake  hose,  a 
troublesome  job  to  do  by  hand,  and  the  pneumatic  car-lifting 


PNEUMATIC   TOOLS. 


551 


Fig.  390  —pull-down  jack. 


Fig.  391.  -SEcriON,  pull-down  jack 


Fig.  392.— section,  pneumatic  moior  s\w. 


552  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

jacks  and  presses  for  putting  car-wheels  on  their  axles,  and  for 
removing  them. 

The  pull-down  jack  is  similar  to  the  lifting  jack,  only  that 
it  has  a  double-acting  piston,  and  its  special  use  is  in  repairing 
cars,  for  removing  draft  timbers  and  sills.  It  is  illustrated  in  side 
view  and  section  in  Figs.  390  and  391.  It  is  moved  on  truck 
wheels  by  a  thill  handle,  and  can  be  used  also  as  a  lift. 

Fig.  392  shows  a  small,  direct-connected  motor  saw,  operated 
in  the  hands  of  workmen.  It  is  used  much  about  the  body  work 
on  cars,  and  for  cutting  off  the  ends  of  car  roofs. 


Chapter  XXV. 


AIR  AS  APPLIED  TO 
PYROMETRY 


AIR    AS   APPLIED    TO    PYROMETRY. 

Air,  unlike  metals,  is  a  perfect  thermometric  or  pyrometric 
substance.  The  action  of  the  air  pyrometer  is  based  on  a  prin- 
ciple which  involves  the  law  of  the  flow  of  air  through  small 
apertures.  The  development  of  the  instruments  has  extended 
over  a  considerable  period  of  time,  and  the  air  pyrometer  has 
been  on  the  market  in  its  present  form  during  the  past  five  years, 
being  now  recognized  as  an  absolute  standard  in  the  determina- 
tion of  high  temperatures. 

Its  application  covers  a  wide  field,  comprising  principally 
the  measurement  and  autographic  recording  of  the  temperature 
of  the  hot  blast,  the  escaping  gas  of  a  blast  furnace,  and  the 
determination  of  the  heat  of  annealing  and  tempering  furnaces; 
by  a  knowledge  and  record  of  which  steel  can  be  treated  accu- 
rately and  with  consistent  results.  It  is  essentially  a  device 
adapted  to  practical  working  conditions,  cannot  be  injured  ex- 
cept through  mechanical  abuse,  and  will  give  the  same  relative 
readings  month  after  month  irrespective  of  whether  it  is  used 
constantly  or  intermittently.  This  last,  together  with  the  fact 
that  it  is  a  recording  pyrometer,  establishes  its  chief  value 
in  industrial  operations,  for  if  the  calibration  of  a  pyrometer 
changes  with  time,  and  the  readings  are  relied  upon  to  regulate 
the  temperature,  even  worse  results  will  be  obtained  than  where 
no  determinations  are  made.  The  record  renders  it  possible 
for  the  one  in  charge  to  know  definitely  whether  or  not  his  in- 
structions are  being  followed,  and  furnishes  a  guide  for  future 
operations. 

The  complete  apparatus  consists  of  three  parts :  the  regula- 
tor, or  main  portion  of  the  instrument;  the  fire  tube,  or  part 
applied  to  the  heat  which  is  connected  with  the  regulator  at 


556 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


any  distance  from  lo  to  300  feet;    and  the   recording  gauge, 
which  is  also  connected  to  the  regulator,  and  by  means  of  which 

a  record  of  the  tem- 
perature is  printed  on 
a  strip  of  paper. 

The  regulators  are 
made  in  two  forms, 
known  as  single  and 
double.  The  first 
permits  of  the  attach- 
ment of  one  fire  tube 
and  one  recording 
gauge,  and  the  second 
of  two  fire  tubes  and 
two  recording  gauges, 
so  that  in  the  latter 
case  the  heat  may  be 
measured  in  two 
places  at  the  same 
time. 

The  fire  tubes  are 
made  in  two  forms, 
blast  furnace  and  port- 
able ;  the  former 
being  used  exclusively 
at  blast  furnaces, 
while  the  latter,  as  im- 
plied by  its  name,  is  at- 
tached to  the  regulator 
by  a  flexible  connec- 
tion which  permits  of 
its  use  at  any  point 
within  a  radius  equal 
to  the  length  of  this  connection.  This  form  of  fire  tube  is 
used  on  annealing  and  tempering  furnaces  and  for  similar  pur- 


FlG.    393.— IHE   AIR   PYROMETER. 


AIR   AS   APPLIED    TO    PYROMETRY.  557 

poses,  the  regulator  and  recording  gauge  being  located  cen- 
trally so  that  the  fire  tube  can  be  inserted  successively  in  any 
one  of  a  number  of  furnaces  or  allowed  to  remain  for  a  greater 
or  less  time  in  any  one  furnace  as  desired.  The  blast-furnace 
fire  tubes  can  be  used  with  either  the  single  or  double  regulator, 
as  can  also  the  portable  fire  tubes. 

The  recording  gauges  vary  only  in  their  calibration,  this 
being  governed  by  requirements.  They  can  be  so  adjusted 
that  the  limiting  lines  of  the  record  shall  be  200°  and  3,000° 
F.,  or  any  intermediate  points  may  be  chosen,  such  as  500° 
and  1,500°,  1,000°,  and  3,000°.  Either  the  Fahrenheit  or  Cent- 
igrade scale  is  obtainable. 

Fig.  393  shows  a  single  pyrometer.  On  the  left  is  the  regu- 
lator, and  connected  to  it  on  the  right  is  the  recording  gauge ; 
a  portable  fire  tube  rests  against  the  recording  gauge.  On  the 
front  of  the  regulator  is  a  scale  graduated  from  100°  to  1,400° 
C,  or  from  200°  to  3,000°  F.  When  the  instrument  is  in  oper- 
ation the  temperature  to  which  the  fire  tube  is  subjected  is 
shown  at  all  times  by  the  water  column  on  front  of  scale. 

Fig.  394  shows  the  recording  gauge.  The  record  is  on  a 
continuous  strip  of  paper,  and  the  scale  is  very  open.  The  rec- 
ords can  be  removed  ever}'  day,  once  a  week,  or  once  a  month 
as  desired,  the  back  record  being  always  accessible  if  the  charts 
are  detached  at  long  intervals. 

As  previously  stated,  the  pyrometer  is  based  on  the  law  gov- 
erning the  flow  of  air  through  small  apertures.  Referring  to 
Fig.  395,  if  two  such  apertures,  A  and  B  respectively,  form  the 
inlet  and  outlet  openings  of  a  chamber,  C,  and  a  uniform  suc- 
tion is  created  in  the  chamber  C  by  the  aspirator  D,  the  action 
will  be  as  follows: 

Air  will  be  drawn  through  the  aperture  B  into  the  chamber 
C,  creating  suction  in  chamber  C,  which  in  turn  causes  air  from 
the  atmosphere  to  flow  in  through  aperture  A.  The  velocity 
with  which  the  air  enters  through  A  depends  on  the  suction  in 
the  chamber  C,  and  the  velocity  at  which  it  flows  out  through 


558 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


B  depends  upon  the  excess  of  suction  in  C  over  that  existing 
in  the  chamber  C,  that  is,  the  effective  suction  in  C.  As  the 
suction  in  C  increases,  the  effective  suction  must  decrease,  and 
hence  the  velocity  at  which  air  flows  in  through  the  aperture 


Fig.  394.— the  rixokder. 

A  increases,  and  the  velocity  at  which  air  flows  out  through  the 
aperture  B  decreases,  until  the  same  quantity  of  air  enters  at 
A  as  passes  out  at  B.  As  soon  as  this  occurs  no  further  change 
of  suction  can  take  place  in  the  chamber  C. 

Air  is  very  materially  expanded  by  heat.     Therefore  the 
higher  the  temperature  of  the  air  the  greater  the  volume,  and 


AIR   AS   APPLIED    TO    PYROMETRY. 


559 


the  smaller  will  be  the  quantity  of  air  drawn  through  a  given 
aperture  by  the  same  suction.  Now  if  the  air,  as  it  passes 
through  the  aperture  A,  is  heated,  but  again  cooled  to  a  lower 
fixed  temperature  before  it  passes  through  the  aperture  B,  less 
air  will  enter  through  the  aperture^  than  is  drawn  out  through 
the  aperture  B.  Hence  the  suction  in  C  must  increase  and  the 
effective  suction  in  C  must  decrease,  and  in  consequence  the 
velocity  of  the  air  through  A  will  increase,  and  the  velocity  of 
the  air  through  B  will  decrease,  until  the  same  quantity  of  air 
again  flows  through  both  apertures.  Thus  every  change  of 
temperature  in  the   air  entering  through  the  aperture  A  will 


D 


B 


'*ii& 


Fig.  395.— the  hkinciple. 

cause  a  corresponding  change  of  suction  in  the  chamber  C.  If 
two  manometer  tubes,  /  and  g  (Fig.  395),  communicate  respec- 
tively with  the  chambers  C  and  C,  the  column  in  tube  q  will 
indicate  the  constant  suction  in  C,  and  the  column  in  tube/ 
will  indicate  the  suction  in  the  chamber  C,  which  suction  is  a 
true  measure  of  the  temperature  of  the  air  entering  through 
the  aperture  A. 

In  its  practical  application  the  aperture  A  (Fig.  395)  must 
be  so  located  that  the  air  before  passing  through  it  shall  acquire 
the  temperature  which  is  to  be  be  measured,  and  this  is  accom- 
plished by  placing  it  at  the  end  of  a  small  platinum  tube  e  (Fig. 
396),  this  being  enclosed  within  a  larger  tube  d  of  the  same 
material,  so  that  the  aperture  A  comes  within  a  short  distance 


560 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


of  the  closed  end  of  the  tube  d  which  protects  it.     Both  tubes, 
d  and  e,  are  brazed  into  drawn  copper  tubes,  c  and  /,  the  length 

of  which  depends  on  the  length 
of  the  water-cooled  jacket  F. 
The  tube  c  is  soldered  into  the 
coupling  piece  c' .  The  tube  / 
terminates  in  a  flanged  head/', 
and  is  secured  to  the  coupling 
piece  c'  by  the  follower  g'  and 
nut  c" .  This  combination  is 
called  the  "fire  tube." 

The  fire  tube  is  placed  within 
a  water-cooled  jacket  F,  which  is 
fed  by  water  entering  at  y  and 
escaping  at  z.  This  jacket  pro- 
tects those  parts  of  the  fire  tube 
that  are  susceptible  to  injury 
by  heat.  The  aperture  A,  being 
thus  disposed,  can  be  readily  lo- 
cated so  that  the  air  must  have 
attained  the  temperature  of  the 
furnace  before  passing  through. 

As  shown  above,  the  air  passes 
in  at  b  and  thence  between  tubes 
d  and  e  through  aperture  A  and 
into   tube   e,    being    drawn    from 

In  order 


>-' 


Fig.  396.— pyrometer  tube  and  plug 

here  to  the  regulator  through  an  air-tight  connection 
that  this  air  shall  be  perfectly  clean  and  thus  avoid  clogging 
the  small  aperture  A,  it  passes  through  a  cotton  filter  before 
going  in  at  b.     This  cleans  it  thoroughly. 

It  is  also  necessary  to  so  locate  aperture  B  (Fig.  395)  that 
before  passing  through  it  the  air  shall  acquire  a  fixed  tempera- 
ture, and  to  provide  for  this  it  is  placed  within  a  coil  and  the 
coil  surrounded  by  steam  at  atmospheric  pressure.  This  se- 
cures a  uniform  temperature  of  212°   F.,   and  the  method  of 


AIR   AS   APPLIED   TO    PYROMETRY. 


561 


arrangement  can  be  seen  in  Fig.  397,  where  B  is  the  aperture, 
G  a  pot  into  which  exhaust  steam  from  the  aspirator  is  led,  and 
t'  the  large-volume  drain  pipe  carrying  off  the  steam  and  con- 
densed water. 

The  operation  of  the  instrument  will  be  understood  by  re- 
ferring to  Fig.  398,  which  is  a  diagrammatic  disposition  of  the 
parts.  The  interior  of  the  pipe,  e,  /,  g,  h,  i,  from  aperture  to 
aperture,  together  with  the  branches  q  and  s,  constitute  the 
chamber  C  of  Fig.  395.  Its  inlet  from  the  atmosphere  is 
through  the  opening  a  at  the  bottom  of  the  filter  /,  and  its 
connection  with  chamber  C  is 
through  the  pipe  i. 

The  aspirator  D  exhausts  into 
the  chamber  G,  keeping  it  at  a 
constant  temperature  of  212°. 
The  steam  and  condensed  water 
escape  through  the  pipe  /  at 
atmospheric  pressure.  Opening 
the  valve  6  steam  enters  the  as 
pirator  D,  and  sucks  the  air 
through  the  tube  m,  out  of  the 
chamber  C,  and  produces  a  suc- 
tion, which  is  kept  constant  by 
the  regulator  H  as  shown  by  the 
manometer  /.  With  a  constant 
suction  in  C  and  cocks  2  and 
4  open,  air  will  enter  at  a,  pass 
through  the  filter  /,  where  it  is 
purified,  then  through  the  con- 
nection /;  into  the  fire  tube.     It 

flows  forward  in  the  space  between  the  two  tubes  ^  and/;  as 
soon  as  it  reaches  the  platinum  tube  d,  which  protrudes  from 
the  cooler,  it  becomes  heated  and  enters  through  the  aperture 
A  into  the  chamber  C,  at  the  temperature  surrounding  the  ex- 
posed end  of  the  fire  tube,  which  is  the  temperature  to  be 
36 


Fig.  397.— steam  heater. 


562 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


FiG     398.  — DETAILS   OF  THE   AIR   PYROMETER. 

Uehling-Steinbart  Company,  Carlstadt,  N.  J. 


AIR   AS   APPLIED    TO    PYROMETRY.  563 

measured.  After  passing  A,  the  air  flows  through  the  pipe  e, 
/,  g,  h,  into  the  coil  /,  where  it  assumes  the  temperature  of 
212°,  at  which  it  passes  through  aperture  B,  thence  by  the  con- 
nection /'  into  the  chamber  C ,  from  which  it  is  drawn  by  the 
aspirator  D  through  m,  and  discharged  with  the  exhaust  steam 
and  condensed  water. 

The  branch  pipes  s  and  q'  connect  respectively  with  the  re- 
cording gauge  L  and  the  manometer  g,  which  is  placed  in  front 
of  the  temperature  scale  on  the  regulator. 

This  detailed  description  of  the  working  principle  of  the 
pyrometer  may  lead  to  the  belief  that  it  is  complicated  and  not 
readily  kept  in  order.  Such  is  not  the  case,  for  it  must  be 
remembered  that  the  only  moving  parts,  aside  from  the  record- 
ing device,  are  steam  and  air.  Wear  is  thus  eliminated,  and 
the  continuous  use  of  the  instruments  under  the  most  adverse 
conditions  attests  their  practical  merit. 

THE    ELECTRIC    CURRENT    INDICATING    METER. 

The  principle  on  which  the  operation  of  these  meters  are 
based  consists  in  causing  the  variations  in  the  electric  current 
to  be  measured  to  control  the  variation  in  pressure  of  a  body  of 
air  in  a  closed  vessel,  this  variation  being  in  turn  indicated  by 
the  rise  and  fall  of  a  column  of  non-volatile  liquid  in  a  glass 
tube,  back  of  which  is  secured  the  scale. 

In  Fig.  399,  assume  that  some  source,  say  a  small  pump,  is 
delivering  air  at  a  fairly  constant  pressure  of  about  if  pounds 
per  square  inch  through  the  pipe  A.  This  enters  the  chamber 
B  and  then  flows  through  a  series  of  porous  diaphragms  made 
of  filter  paper  whose  function  is  to  serve  as  an  air  resistance, 
incidentally  serving  to  remove  any  dust  particles.  The  air 
then  enters  the  passage  D  into  which  is  drilled  the  opening  E 
which  is  capped  by  the  valve  F. 

The  valve  consists  simply  of  a  small  flat  disc  of  non-oxidiza- 
ble  metal  F  resting  on  a  circular  seat  with  escape  ports  G  below 


564 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


Fig.  399.— column  type,  electric  current  indicating  meter. 
Machado  &  Roller,  New  York  City. 


AIR    AS    APPLIED    TO    PYROMETRY.  565 

it  and  a  pin  77  resting  on  top.  On  the  pin  rests  a  spool  y  car- 
ried by  one  end  of  the  lever  /,  on  the  other  end  of  which  is  a 
counter-weight  K,  by  means  of  which  the  effective  weight  on 
the  pin  H  can  be  adjusted. 

The  spool  is  wound  with  wire  through  which  the  current  to 
be  measured  is  passed,  this  being  done  via  the  two  short  thin 
copper  ligaments  L  which  support  and  form  the  pivots  about 
which  the  lever  can  oscillate. 

A  magnet  J/  furnishes  a  field  of  force  such  that  the  reaction 
between  it  and  the  current  pimels  the  spool  down  with  a  force 
increasing  as  the  current  increases.  The  valve  F\&  thus  a  vari- 
ably loaded  safety-valve  whose  blowing-off  point  is  constantly 
and  proportionately  varied  by  the  current  variation.  The 
counter-weight  K  on  the  lever  is  so  adjusted  that  when  no  cur- 
rent is  passing  through  the  spool  the  weight  on  the  valve  pin 
is  such  that  the  blowing-off  pressure  in  D  is  sufficient  to  force 
the  liquid  in  the  closed  chamber  ^  up  through  the  glass  tube 
6?  to  a  height  R,  which  therefore  is  the  zero  of  the  scale.  The 
pressure  cannot  go  above  this  when  no  current  is  on,  as  any 
tendency  to  increase  simply  results  in  lifting  the  valve  .slightly 
higher,  whereupon  more  air  escapes  and  the  pressure  falls  back ; 
nor  can  it  go  lower,  for  if  there  were  this  tendency  the  valve 
would  partially  close  because  of  the  spool  weight,  and  the  less 
rapid  escape  of  air  through  it  would  cause  the  pressure  to  build 
up  again  because  of  the  constant  flow  of  air  from  the  high- 
pressure  supply  at  A  through  the  air  resistance  C. 

Exactly  the  same  thing  holds  good  when  the  weight  on  the 
valve  is  that  due  to  the  non -counterbalanced  portion  of  the 
spool  weight  plus  the  downward  thrust  caused  by  a  given  cur- 
rent through  it.  This  gives  what  is  practically  a  heavier  loaded 
safety  valve,  so  that  the  blowing-off  pressure  in  N  is  higher,  and 
this  higher  pressure  of  course  forces  the  liquid  up  further  in 
the  glass  tube,  thus  showing  the  presence  of  a  current.  The 
height  to  which  the  liquid  rises  is  directly  a  measure  of  that 
current,  because  the  extra  downward  thrust  on  the  spool  is. 


566 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


from  the  magnetic  field  and  spool  design,  proportionate  to  the 
current. 

The  air  resistance  C  not  only  prevents  the  action  from  being 
so  sudden  that  the  indications  are  not  dead-beat,  but  in  the  case 
of  a  decrease  in   current  strength  allows  the  air  in  the  closed 

chamber  .V  to  flow 
back  promptly  and  so 
register  the  decrease. 
The  glass  tube  being 
but  24  inches  long,  the 
pressure  at  A  (equiva- 
lent to  about  a  49-inch 
column  of  the  liquid) 
is  always  sufficiently  in 
excess  of  that  in  the 
passage  D  and  the 
chamber  .Vto  cause  the 
changes  to  be  promptly 
registered. 

From  the  foregoing 
it  is  seen  that  the  zero 
adjustment  is  made  by 
screwing  in  or  out  the 
counter-weight  A',  thus 
shifting  all  scale  values 
an  equal  distance  up 
or  down  the  tube.  For  actual  calibration  before  shipment  an 
iron  screw  .S  of  heavy  cross-section  is  provided,  which,  on  being 
brought  closer  to  or  further  from  the  opposite  leg  of  the  mag- 
net, weakens  or  strengthens  the  field  in  which  the  active  spool 
works  by  shunting  a  portion  of  the  lines. 

It  should  also  be  noted  that  the  only  work  that  the  varying 
current  has  to  perform  is  to  control  the  air  pressure. 

To  furnish  the  air  required  for  the  operation  of  the  column 
type  of  instruments,  this  is  one  of  two  separate  types  of  devices. 


Fig.  400.— electric  air  compressor. 


AIR    AS   APPLIED    TO    PYROiMETKY.  567 

The  first  is  a  simple,  single-cylinder,  single-acting  air  pump, 
mounted  on  a  square  iron  box  which  serves  as  an  air  reservoir, 
and  driven  by  a  one-twentieth  horse-power  motor  suspended 
underneath  and  connected  to  the  pump  by  a  belt.  This  type  is 
of  sufficient  capacity  to  run  fifty  indicators  or  twelve  recorders, 
the  construction  of  the  latter  being  such  that  they  require 
nearly  four  times  as  much  air  as  the  former. 

The  motor  is  furnished  for  either  a  i  10  or  a  220  volt  circuit, 
and  for  either  direct  or  alternating  current,  as  may  be  desired. 

The  second  type  is  a  water-operated  compressor,  which 
operates  like  an  injector,  the  water  carrying  the  air  with  it  and 
compressing  it  to  the  desired  point.  These  require  about  ten 
gallons  of  water  per  hour  per  instrument,  with  3-foot  head, 
and  are  built  in  sizes  to  suit  the  particular  installation. 

THE    COMPRESSED-AIR    ELECTRIC    RECORDING    METER. 

This  is  the  same  in  principle  as  the  indicating  type  de- 
scribed on  the  preceding  pages.  Instead,  however,  of  employ- 
ing a  rising  and  falling  liquid  column  in  a  glass  tube  to  give 
visual  indications  of  the  current  changes,  the  column  is  made  of 
much  larger  diameter  and  carries  a  hollow  float  supporting  a 
rod  with  a  pen  at  the  extremity  thereof,  which  in  turn  traces  a 
line  on  a  sheet  of  paper  carried  before  it  by  a  clock  movement. 

By  making  the  column  diameter  of  a  proper  size  the  pen 
friction  becomes  negligible  compared  to  it,  and  the  pen  can  be 
made  to  carry  a  supply  of  ink  sufficient  for  long  records  without 
having  this  varying  weight  destroy  the  accuracy  of  the  indica- 
tions. 

The  illustration  (Fig.  401)  gives  a  section  of  this  recorder, 
similar  parts  being  lettered  the  same  as  those  in  Fig.  399.  It 
will  be  noted,  as  above  stated,  that  the  only  additions  comprise 
the  float  P,  the  rod  Q,  and  the  pen  R,  together  with  the  drum 
S,  which  is  rotated  one  inch  an  hour  by  internally  placed  clock- 
work, and  to  the  surface  of  which  is  secured  the  record  paper. 


568 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


f'^C\vvvvvvvvv\vvvv^^^kv^vvv^v^^v-'.vwv^^^^'v^'v<^<'^:'??^::'?cU 


Fig.  401.— section  of  the  volt  and  ampere  recording  and  indicating  meter. 


AIR    AS    APPLIED    TO    PYROMETRY.  569 

Particular  attention  is  invited  to  the  fact  that,  owing  to  the 
absolutely  dead-beat  indications  which  this  class  of  apparatus 
gives,  the  meters  never  run  over;  i.e.,  any  fluctuations  shown 
by  them  are  true  fluctuations,  and  their  values  are  not  added  to 
by  the  inertia  of  the  moving  parts. 

Another  unique  feature  that  these  devices  possess  is  this : 
By  drilling  an  additional  hole  through  the  cap  forming  the  top 
of  the  chamber  in  which  the  liquid  is  contained,  and  connecting 
this  by  a  tube  with  a  second  closed  vessel  U,  similar  to  N  in 
Fig.  399,  the  liquid  in  the  tube  dipping  into  this  vessel  will  rise 
and  fall  with  the  rise  and  fall  of  the  pen,  as  the  variation  in  the 
pressure  of  the  air  therein  is  the  same  as  that  in  the  recorder 
chamber.  In  this  way  it  is  possible  to  put  the  recorders  them- 
selves in  the  superintendent's  office  or  elsewhere  so  that  they 
cannot  be  tampered  v;ith,  and  place  the  pilot  indicator  on  the 
switchboard  so  that  the  attendant  will  have  before  him  a  con- 
stant indication  of  what  the  recorder  is  doing. 

The  sole  manufacturers  of  the  pyrometric  and  pneumatic 
volt  and  ampere  meters  are  the  Uehling-Steinbart  Company,  of 
Carlstadt,  N.  J. 


Chapter  XXVI. 


COMPRESSED  AIR  IN 
RAILWAY  SERVICE 


COMPRESSED   AIR    IN    RAILWAY   SERVICE. 

It  is  now  forty  years  since  compressed  air  for  street-railway 
propulsion  was  agitated  and  began  to  take  on  form  in  plans  for 
putting  this  system  into  practical  operation.  Although  high 
air  pressures  had  then  and  previously  been  produced  in  an  ex- 
perimental way,  the  high-storage  pressures  of  the  present  time 
were  then  scarcely  dreamed  of  for  practical  work.  The  air- 
propulsion  schemes  seem  to  have  slumbered  until  Captain 
Beaumont  started  a  compressed-air  passenger  car  with  rising 
storage  pressures  that  finally  reached  i,ooo  pounds,  at  which 
the  conditions  of  receiver  construction  for  storage  seemed  to 
have  reached  a  limit.  At  this  time  (1876),  Mekarski  was  advo- 
cating and  putting  into  practice,  in  France,  the  system  of  re- 
heating by  hot  water  and  using  the  evaporated  water  at  high 
temperatures  with  the  air,  and  on  this  system  mine-hauling 
locomotives  were  operated.  The  first  air-motor  car  was  run  in 
Paris  in  1876.  This  was  soon  followed  by  the  building  of  com- 
pressed-air railways  at  Nantes,  the  suburban  roads  of  Vincennes 
and  Nogent  near  Paris.  In  1890  the  Berne,  vSwitzerland,  city 
and  suburban  railways  were  opened  for  operation.  The  storage 
pressure  there  used  was  470  pounds,  while  the  car-storage  press- 
ure was  limited  to  440  pounds  per  square  inch.  An  extended 
investigation  of  the  operating  expenses  of  this  road  was  made 
at  that  time,  and  was  found  very  favorable  to  the  compressed-air 
system,  being  17  cents  per  car  mile. 

The  conclusions  derived  from  the  investigation  of  the 
Mekarski  system  at  Berne  for  urban  and  suburban  tramway 
traffic  consisted  in  the  pleasing  appearance  of  the  motor  cars, 
in  the  absolutely  smooth  and  noiseless  motion,   and  the  total 


574 


COMPRESSED    AIR    AND    ITS    APl'LICATIONS. 


absence  of  smoke,  steam,  or  heat;  that  it  had  fully  vindicated 
this  system  as  preferable  to  any  other  system  of  tramway  trac- 
tion. At  Marseilles,  France,  the  compressed-air  tramway  stor- 
age pressure  is  1,200  pounds  per  square  inch. 

The  reheaters  of  this  system  are  illustrated  in  the  chapter 
on  reheating.  The  Hardie  system  was  first  on  trial  on  the 
Second  Avenue  Railroad  in  1879  (Fig.  402). 

This  system  was  started  in  Toledo,  Ohio,  and  in  Westfield, 


Fig.  402.— compressed-aiu  motor  passenger  car,  on  second  avenue, 

NEW  YOKK.      1879-80. 

Mass.,  about  1892,  but  from  some  constructive  difficulties  was 
changed  to  electric  propulsion. 

The  Judson  system  was  originally  instituted  in  a  revolving 
drum  under  the  track,  driven  in  sections  by  compressed-air 
motors  with  air  compressed  in  a  central  station  and  distributed 
to  the  motors  through  an  underground  pipe  system.  This  fail- 
ing in  expectations,  the  Judson  system  was  changed  to  direct 
motor  traction  with  the  air  heated  by  a  small  furnace  containing 
a  coiled  pipe  near  the  motor,  in  which  the  air  was  reheated  after 
passing  the  reducing  pressure  valve,  thus  giving  the  best  effect 
of  reheating  in  the  economy  of  air  power. 

This  system  finally  gave  way  to  the  Hardie  improvements 
on  the  Mekarski  system,  and  is  now  in  use  in   Chicago,  111., 


COMPRESSED    AIR   IN    RAILWAY    SERVICE. 


575 


Fig.  404.— thf  judson  system  in  Chicago,  ill.    motor  passenger  car  and  trailer. 


576 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


with  passenger  motor  cars,  with  or  without  trailers  to  suit  the 
necessity  for  traffic  accommodation. 

In  Fig. 406  are  represented  some  details  of  these  motor  cars, 
in  which  the  piston  in  the  cylinder  H  is  connected  by  rod  with 
a  rock  shaft  for  transferring  the  line  of  force  to  the  outside  of 


j5  -a 


.     .::   r.  bt, 


u         O    .„     cS 


e  S6 


3  ^   ^   o 


2J  M 


the  wheels  through  the  connecting  rod  /"pivoted  to  the  parallel- 
rod  connection  to  the  fore  and  aft  wheel  cranks.  L  is  the  brake 
cylinder,  and  F  one  of  the  high-pressure  bottles.  M  M  are 
columns  in  which  are  placed  the  controlling  gear  with  their 
handles  at  N. 


COMPRESSED    AIR    IN    RAILWAY    SERVICE. 


577 


-^^ 


A 


1::^.: 


t"-=«r:r 


/-> 


Mi 


In  Fig.  407  is  illustrated  a  section 
of  the  Hardie  motor  car  of  the  type 
used  on  125th  Street,  New  York  City, 
showing  the  location  of  the  high- 
pressure  air  tanks  B,  C,  D,  E,  F,  and 
the  reheating  tank  A ;  the  reducing 
valve  at  G  and  the  motor  cylinder  at 


Fig,  407.— section,  hardie  motor  car. 

H.  The  air  passes  from  the  high- 
pressure  tanks  to  the  reducer,  then  to 
the  reheater,  discharging  beneath  the 
water  and  taking  on  its    temperature, 


^  Fig.  408.— the  air-pressure  card. 

and  is  saturated  with  vapor  at  a  press- 
ure of   150  pounds;    then  to   the   con- 
trolling valve  and  expanded  in  the  cyl- 
inders to  near  the  atmospheric  pressure  under  normal  condi- 
tions of   running.      In   Fig.   408    is    an    indicator    card    from 
37 


578 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


ItlOU 


3   s 


COMPRESSED   AIR   IN    RAILWAY    SERVICE.  579 

these  motors  showing  a  mean  pressure  of  about  40  pounds 
at  ^  cut-off. 

In  Fig.  409  are  detailed  a  plan  and  elevation  of  a  Hardie 
motor  car,  the  various  parts  of  which  may  be  measured  by  the 
figured  scale  of  the  elevation,  and  in  Fig.  405  an  outside  view 
of  the  same  style  of  car  now  running  on  the  28th  and  29th 
Streets  line  of  the  Metropolitan  Railway  Company,  New  York 
City.  Similar  cars  are  running  on  the  street  railway  system  at 
Rome,  N.  Y. 

The  motor  cars  of  the  Compressed  Air  Company,  New 
York  City,  are  similar,  in  size  and  appearance,  to  standard  elec- 
tric or  cable  cars,  and  can  be  operated  at  any  desired  speed. 
The  type  of  car  now  in  operation  weighs  about  22,000  pounds. 
All  its  machinery  and  storage  apparatus  are  placed  below  the 
body  proper.  The  motor  and  storage  are  supported  and  carried 
on  independent  frames  and  springs  which  relieve  the  axle  of 
all  pounding  and  hammering  on  the  track.  ; 

The  engines  of  these  cars  have  two  cylinders,  7-inch  diame- 
ter, 14-inch  stroke,  with  driving-wheels  of  16-inch  diameter. 
They  are  equipped  with  air  brakes  operated  by  the  same  air 
that  runs  the  motors.  The  operating  levers  are  placed  on  the 
platforms,  are  simple  in  form,  and  of  such  design  that  no  con- 
fusion can  arise  in  the  manipulations  of  the  operator. 

The  storage  apparatus  consists  of  sixteen  air  reservoirs, 
having  a  total  capacity  of  51  cubic  feet  and  weighing  4,340 
pounds.  One  of  these  is  placed  under  each  seat,  running  the 
entire  length  of  the  car.  The  others  are  arranged  beneath  the 
floor  of  the  car,  and  all  of  them  rest  on  a  framework  of  locomo- 
tive construction  supported  on  the  usual  type  of  locomotive 
springs.  The  framework  also  supports  a  heater  7  feet  long 
and  19  inches  in  diameter  that  contains  500  pounds  of  hot 
water,  through  which  the  air  passes  on -its  way  to  the  motors. 

This  type  of  car  has  run  17  miles  on  one  charge  of  air,  but 
is  rated  as  having  a  capacity  of  12  miles,  anything  over  that 
being   reckoned    as   margin   to  allow   for  emergencies,    heavy 


58o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


z  o 


COMPRESSED    AIR   IN    RAILWAY    SERVICE.  58 1 

loads,  frequent  stops,  bad  tracks,  etc.  Its  normal  speed  is  12 
miles  an  hour,  but,  like  the  steam  locomotive,  it  can  be  oper- 
ated at  any  required  speed. 

In  Fig.  411  are  detailed  the  proportions  of  the  reheater 
used  in  the  cars  of  the  Metropolitan  line,  28th  and  29th  Streets, 
New  York  City.  It  will  be  seen  that  the  air  after  pressure 
reduction  to  the  working  limit,  150  pounds,  is  delivered  to  the 
reheater  through  a  perforated  pipe  lying  on  the  bottom  of  the 
cylinder  and  beneath  the  hot-water  surface.  Baffle  plates  are 
placed  across  the  cylinder  to  prevent  the  water  from  swashing 
on  starting  and  stopping  the  car.  A  perforated  pipe  T  along 
the  top  of  the  cylinder  conveys  the  air,  reheated  at  the  reduced 
pressure,  to  the  throttle  valve  on  the  platform  and  from  thence 
to  the  cylinder. 

In  Fig.  412  is  shown  the  elevation  and  end  view  of  the 
motor  gear  with  an  outside  cylinder  connected  directly  with  the 
crank  pin  on  the  wheel.  The  other  wheel  is  connected  by  an 
extension  of  the  wheel  crank  pins  and  an  outside  connecting 
rod.  The  rocker  arm  ^  is  operated  by  a  link  /,  pivoted  to  the 
slide  and  oscillating  on  the  pivot  /,  fixed  to  the  frame  and  also 
connected  by  a  link  to  the  arm/,  which  is  pivoted  to  the  cut-off 
valve  at  ui,  and  to  an  extension  of  the  wrist  pin  on  the  double 
rocker  arm  a,  which  is  operated  by  a  sector  slide  linked  to  cams 
on  the  wheel  shaft;  so  that  the  main  valve  and  cut-off  have 
variable  motion  in  both  forward  and  backward  running. 

It  is  apparent  from  Fig.  413  that  the  reducing  valve  is  a 
diaphragm  valve,  specially  constructed  to  deal  with  high  press- 
ure, and  that,  in  addition  to  the  ordinary  action  of  such  valves,  a 
supplementary  action  is  brought  about  by  reducing  the  air  press- 
ure that  is  normally  kept  above  the  valve  head  in  chamber  A. 
In  ordinary  action  this  v^alve  graduates  air  to  150  pounds. 
When  it  is  desired  quickly  to  accelerate  under  heavy  load,  a 
movement  of  the  brake-valve  handle  to  a  given  position  dis- 
charges the  air  from  chamber  A  ;  this  increases  the  value  of 
the  coil  spring  beneath  the  diaphragm,  opening  the  reducing 


582 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


IL 


ii"ii 


'^^ 


::\ 


\-^ 


COMPRESSED    AIR    IN    RAILWAY    SERVICE. 


583 


valve  in  greater  measure,  and  temporarily  increases  the  working 
pressure  to  200  pounds  per  square  inch,  while  it  is  desirable  to 
use  that  pressure  in  the  cylinders. 

Fig.  414  illustrates  the  operation  of  the  air  brake  of  the 


Fig.  413.— detail  section  of  keducing  valve. 


Hardie  motor  car.     The  brake  piston  rod  is  hollow,  and  thus 
forms  a  cylinder  within  the  brake  cylinder. 

In  the  illustration  the  piston  is  shown  in  the  set  position, 
and  the  motorman's  brake  valve  would  be  in  service  applica- 


584 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


tion.  Braking  force  is  applied  by  admitting  air  to  the  annular 
space  marked  R.  When  release  is  made  the  air  passes  from 
the  point  T  through  a  by-pass  and  the  release  valve  to  the  point 
Vin  the  rear  of  the  piston,  and  pressure  is  thus  exerted  upon 
the  greater  area  of  the  total  diameter  of  the  piston  head.     The 


Fig.  414.— the  brake  cylinder. 

difference  in  pressure  area  will  therefore  restore  the  piston  to 
the  release  position  and  the  air,  thus  applied  in  releasing, 
bleeds  through  the  opening  S  and  out  of  the  hollow  piston 
through  numerous  ports,  W,  to  atmosphere,  the  bleeding  action 
being  so  free  as  to  be  practically  noiseless. 

The  first  compressed-air  locomotive  for  lona  Island,  N.  Y., 
to  furnish  motive  power  for  cars  containing  ammunition,  under 
contract  with  the  United  States  Government,  has  been  com- 
pleted at  the  H.  K.  Porter  Locomotive  Works.  It  is  the  type 
of  locomotive  decided  upon  for  moving  railroad  cars  about  the 
vast  magazines  which  are  the  storehouses  for  ammunition  used 
in  the  coast  defences  and  forts  throughout  the  country.  The 
engine  now  finished  is  a  novel  one,  and  was  ordered  together 
with  a  complete  plant  for  charging  and  operating. 

In  event  of  the  new  locomotive  proving  a  success  and 
standing  the  tests  that  it  will  be  put  to,  the  Government  will 
order  a  number  of  others  like  it,  all  to  be  used  on  the  same 
island.  lona  Island  is  probably  the  greatest  storehouse  for  ex- 
plosives that  is  owned  by  the  United  States.     It  is  situated  in 


COMPRESSED   AIR    IN    RAILWAY    SERVICE. 


585 


the  Hudson  River,  a  short  distance  from  New  York,  and  from 
it  ordnance  and  ammunition  are  sent  out  to  the  various  points 
along  the  coast.  For  a  long  time  the  handling  of  explosives 
has  been  done  with  mules,  dragging  cars  and  carts.  It  has 
been  a  slow  and  tedious  process,  as  well  as  a  costly  one.  The 
island  is  covered  with  a  series  of  railroad  tracks,  and  cars  from 
the  West  Shore  Railroad  are  used  in  shipping  material,  being 
loaded  and  moved  about  by  teams.  It  is  absolutely  necessary 
that  there  should  be  no  fire  of  any  kind  near  the  storehouses  of 
the  ammunition. 

The  success  that  attended  the  use  of  compressed-air  locomo- 
tives in  the  great  plant  of  the  California  Powder  Company,  near 
San  Francisco,  drew  the  attention  of  the  army  officials  to  the 
availability  of  compressed-air  traction  for  lona  Island,  and  after 
much  planning  the  first  plant  was  ordered.     This  consists  of 


Fig. 


-THE    HAKDIE   COMPRESSED- AIR  LOCOMOTIVE. 


one  locomotive  capable  of  handling  standard  railroad  cars,  a 
series  of  charging  stations  along  the  lines  of  the  rails  for 
charging  the  locomotives  whenever  it  is  necessary,  and  a  com- 
plete power  plant  for  operating  the  compressors. 

The  new  locomotive  is  said  to  be  one  of  the  largest  of  its 


586  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

kind  ever  built.  It  will  run  several  miles  without  being  re- 
charged, and  can  be  charged  with  air  at  any  one  of  the  numer- 
ous stations  in  less  than  thirty  seconds.  There  being  no  fire 
of  any  kind  about  the  locomotives,  there  is  not  the  least  danger 
from  explosion. 

THE    COST   OF   COMPRESSED-AIR   RAILWAY    SERVICE. 

From  the  few  compressed-air  railways  in  which  the  entire 
plant  has  been  built  for  a  specific  amount  of  service,  accurate 
returns  of  cost  of  operating  as  compared  with  the  same  service 
of  other  systems  of  locomotion  have  been  meagre  and  im- 
satisfactory. 

The  cost  of  operating  the  air  plant  on  the  Nantes,  France, 
railway  has  been  stated  at  12  cents  per  car  mile.  It  is  fifty- 
eight  miles  in  length  and  has  gradients  of  four  per  cent. 

The  cost  of  operating  the  air  plant  on  the  Berne,  Switzer- 
land, tramway  has  been  given  as  17  cents  per  car  mile.  The 
road  is  two  miles  or  more  in  extent  and  has  gradients  of  over 
five  per  cent,  necessitating  heavier  power  motors  than  for  lower 
grades. 

On  the  125th  Street  line  in  New  York  the  compressed-air  cars 
were  switched  in  between  the  cable  cars  and  were  limited  to  their 
regular  speed,  not  being  favored  by  conditions  for  clean  runs. 
The  frequent  stops  made  necessary  by  city  traffic  counted  against 
the  best  conditions  for  cost  of  service,  and  made  the  volume  of 
air  used  larger  than  for  a  less  obstructed  service.  The  steepest 
grade  on  this  line  is  ^ .']  per  cent,  which  for  only  a  short  run 
necessitates,  as  stated  for  the  Berne  plant,  a  heavier  motor  power 
than  for  more  even  grades.  The  cars  actually  operated  on  this 
line  were  two;  but  the  installation  was  made  for  a  larger  num- 
ber, which  brought  the  operating  cost  to  an  excessive  figure, 
viz.,  20  cents  per  car  mile.  On  the  basis  of  a  larger  number  of 
cars,  suitable  for  the  compressed-air  installation,  the  cost  has 
been  estimated  at  less  than  17  cents  per  car  mile.     With  the 


COMPRESSED   AIR   IN    RAILWAY    SERVICE. 


587 


improvements  of  service  now  being  done  the  cost  should  fall 
to  about  13  cents  per  car  mile.  The  average  consumption  of 
free  air  per  car  mile  on  the  125th  Street  line  has  averaged  dur- 
ing seven  months'  service  477  cubic  feet  per  car  mile.  The 
operation  of  the  air  cars  on  the  28th  and  29th  Streets  line  has 
not  yet  given  sufficient  data  in  regard  to  cost,  as  the  compress- 
ing plant  largely  exceeds  the  present  needs  of  the  car  plant. 

It  has  been  estimated  that  the  actual  cost  of  compressing  air 
to  2,500  pounds  pressure  per  square  inch,  and  storing  for  use  in 
a  modern  air-compressing  plant  operated  with  condensing  en- 
gines, including  coal  at  $2.75  per  ton,  water  at  $1  per  1,000  cubic 
feet,  oil  and  waste,  the  removal  of  ashes,  labor,  repairs,  and 
maintenance  of  power  plant,  depreciation  and  interest  on  cost  of 
entire  power-plant  including  buildings,  for  compressing  plants 
of  the  following  capacities,  based  on  the  consumption  of  2^ 
pounds  of  coal  per  hour  per  horse  power  for  twenty  hours  per 
day,  will  not  exceed  the  following  figures: 

Cost  per  1,000  cubic  feet  of  free  air  compressed  to  2,500 
pounds  pressure  per  square  inch : 


Station  capacity. 
500  cubic  feet  per  minute 
1,000 
2,000 
3,000 
4,000 
5,000 


Cost. 
.$0.0675 

.  .0571 
.  0469 
.0419 

•  -0394 

•  -0375 


Station  capacity. 
6,000  cubic  feet  per  minute 
7,000  "  " 

8, 000  "  " 

9,000  "  " 

10.000  "  " 


Cost. 
$0.0359 
.0342 
.0326 
■  0312 
.0300 


Responsible  parties  will  guarantee  that  the  cost  will  be  less 
than  stated,  and  the  writer  believes  that  the  cost  in  highest- 
grade  plants  can  be  reduced  fully  25  per  cent,  from  the  above 
figures. 


COMPRESSED    AIR    FOR    UNDERGROUND    HAULAGE. 

The  use  of  compressed  air  for  underground  haulage  was 
probably  given  its  first  practical  application  in  the  St.  Gothard 
tunnel  in  1873  and  on,  until  the  tunnel  was  finished.  The  initial 
pressure  then  used  was  only  210  pounds  in  the  main  tank,  re- 


588  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

duced  to  a  working  pressure  of  60  pounds  in  the  secondary 
tank.  High  pressures  had  not  then  entered  the  realm  of  the 
practical  use  of  compressed  air ;  but  the  early  pneumatic  loco- 
motives did  good  work.  The  modern  application  of  compressed 
air  in  mine  haulage  is  exemplified  in  the  operation  of  pneu- 
matic locomotives  in  the  mines  of  the  Susquehanna  Coal  Com- 
pany at  Glen  Lyon,  Pa.,  where  there  are  two  compressed-air 
motors  in  operation.  The  air  is  supplied  by  a  compressor  of 
the  three-stage  type,  having  steam  cylinders  20x24  inches 
and  air  cylinders  I2ix9i  and  5  X24  inches,  with  water-jackets 
and  intercoolers,  compressing  the  air  to  600  pounds  per  square 
inch.  The  air  passes  through  a  line  of  5 -inch  special  strong  pipe 
200  feet  to  the  head  of  the  shaft,  down  the  shaft  800  feet,  and 
then  along  the  gangway  about  3,400  feet,  a  total  length  of  4,300 
feet.  This  pipe  line  has  a  capacity  of  580  cubic  feet  and  acts 
as  a  reservoir  for  the  compressor.  It  is  coupled  together  with 
threaded  sockets  which  are  counterbored  for  a  lead  filling,  which 
is  calked.  At  intervals  of  about  200  feet,  and  at  all  valves  and 
charging  stations,  flange  couplings  are  used  with  lead  gaskets. 
The  line  is  perfectly  tight,  being  tested  to  1,500  pounds  per 
square  inch.  Charging  stations  are  placed  where  required,  and 
consist  of  a  universal  metallic  coupling  which  is  attached  to  the 
check  valve  of  the  locomotive  air  tanks  when  a  fresh  supply  of 
air  is  required.  It  requires  about  one  and  one-half  minutes  to 
complete  the  operation  of  charging  the  locomotive,  and  reduces 
the  pressure  in  the  main  pipe  line  from  600  pounds  per  square 
inch  to  about  570  pounds  per  square  inch.  A  charge  of  air 
weighs  about  380  pounds.  The  locomotive  is  of  the  four-wheel 
type,  having  cylinders  7  inches  diameter  by  14-inch  stroke; 
drivers,  24  inches  diameter;  weight,  18,500  pounds;  length 
over  all,  17  feet  6  inches;  width,  5  feet  2  inches;  height,  5  feet. 
The  air  for  propelling  the  locomotive  is  stored  in  two  cylin- 
drical steel  tanks  with  a  combined  capacity  of  130  cubic  feet 
and  supported  by  cast-iron  saddles  resting  on  the  frames  of  the 
locomotive.     The   air   flows   from   the   main    tanks    throusfh   a 


COMPRESSED   AIR   IN   RAILWAY    SERVICE.  589 

specially  designed  reducing  valve  into  an  auxiliary  reservoir, 
and  from  thence  through  a  throttle  valve  to  the  cylinders.  The 
pressure  in  the  auxiliary  reservoir  can  be  regulated  anywhere 
from  30  pounds  up  to  140  pounds  or  150  pounds  per  square 
inch  as  required.  The  air  in  the  auxiliary  reservoir  is  main- 
tained at  a  constant  pressure,  while  in  the  main  storage  tanks 
it  may  vary  from  570  pounds  per  square  inch  down  to  the  press- 
ure at  which  the  reducing  valve  is  adjusted;  when  this  press- 
ure is  reached  in  the  main  storage  tanks  the  air  passes  through 
to  the  cylinders  without  further  reduction  in  pressure. 

The  locomotive  hauls  sixteen  empty  cars  a  distance  of  3,700 
feet  into  the  gangway  and  returns  to  the  shaft  sixteen  loaded 
cars  with  one  charge  of  air,  starting  with  a  pressure  of  575 
pounds  per  square  inch  and  ending  with  about  100  pounds  per 
square  inch.  The  train  of  empty  cars,  including  the  locomo- 
tive, weighs  60,000  pounds,  and  the  train  of  loaded  cars,  in- 
cluding the  locomotive,  weighs  166,000  pounds.  The  grades 
favor  the  loads.  The  locomotive  runs  from  twenty-five  to  fifty 
miles  per  day,  depending  upon  the  length  of  trip  and  time  con- 
sumed in  making  up  the  trains  at  the  terminals.  This  locomo- 
tive was  lowered  down  the  mine  shaft  a  vertical  distance  of  800 
feet  without  dismantling  in  any  manner. 

PNEUMATIC  MINE  LOCOMOTIVES  OF  THE  BALDWIN  LOCOMOTIVE 

WORKS. 

The  new  modification  of  the  pneumatic  locomotives  of  this 
company  is  shown  in  Figs.  416  to  419,  an  advance  in  air- 
motor  design  in  the  ribbed  compound  cylinders. 

Pneumatic  locomotives  for  mine  haulage  have  been  in  use 
for  several  years,  and  are  to-day  a  standard  product  of  all  the 
large  steam  locomotive  builders.  They  possess  several  features 
which  make  them  ideal  for  mining  purposes  and  most  suitable 
for  quite  a  variety  of  surface  work,  generally  industrial  opera- 
tions, such  as  plantations,  tunnels,  powder  mills,  lumber  yards, 


590 


COMPRESSED    AIR   A\D    ITS   APPLICATIONS. 


Fig.  416.  -COMPOUND  pnkumaiic  locomotive. 

Six- wheel  type.     Compound  cylinders,  ribbed  for  the  absorption  of  heat  from  the  outer  air, 
thus  preventing  extreine  cold  in  the  exhaust.     Built  for  the  H.  C.  Frick  Coal  Company. 

textile  manufactories,  cotton  mills,  storage  warehouses,  and 
other  places  where  the  risk  of  fire  resulting  from  sparks  and 
the  freedom  from  other  objectionable  features  make  the  corn- 


ed. 


Fig.  417.— compound  pneum.\tic  locomotive. 

Four-wheel  type.     Ribbed  cylinders.    Built  for  the  Philadelphia  and  Reading  Coal  and  Iron 

Company. 

pressed-air  locomotive  a  most  desirable  and  satisfactory  means 
of  hauling. 

Compressed-air  power  has  marked  advantages  over  any  other 
kind  of  haulage  power  for  mines  and  constructive  works,  where 


Fig.  41S.— pneu.m.\tic  mine  locomoiive. 
Two-cylinder,  four-wheel  type. 


COMPRESSED    AIR    IN    RAILWAY    SERVICE. 


591 


the  entanglements  of  electric  wires  and  stays  are  always  in  the 
way,  and  steam  is  a  nuisance.  Compressed-air  power  is  a  free 
traveller  to  2fo  wherever  a  track  is  laid  and  even  without  tracks 


Fig.  419.— single-tank  pneumatic  locomotive. 
Baldwin  Locomotive  Works. 

in  the  compressed-air  driven  truck.  The  distance  run  with  one 
charge  of  air  is  only  limited  by  the  capacity  of  the  storage 
tanks,  and  since  high  initial  pressure  has  become  available,  the 
limit  of  usefulness  has  been  largely  extended. 

COMPRESSED-AIR    LOCOMOTIVES    FOR    HAULAGE. 

The  mule,  which  has  so  long  been  used  for  hauling  in  mines 
and  in  yard  work,  has  nearly  lost  his  calling  by  the  successful 
adoption  of  the  more  powerful  agent,  compressed  air,  in  the 


Fig.  420.— pneumatic  locomotive  for  yard  and  factory  service. 

diminutive  narrow-gauge  locomotive  that  needs  no  feed  when 
no  work  is  being  done.  The  compressed-air  system  has  en- 
tirely supplanted  steam  in  underground  work,  and  has  become 


592 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


a  most  economical  competitor  of  both  steam  and  electricity  in 
yard  and  factory  haulage. 

Fig.  421  represents  a  type  of  yard  locomotive  of  the  H.  K. 
Porter  Company,  Pittsburg,  Pa.,  designed  for  factory  and  yard 
work.  It  is  built  for  narrow  gauge  and  with  wheel  base 
as  short  as  3  feet  6  inches,  and  for  curves  of  12  feet  radius. 
The  single  air  tank  carries  a  maximum  pressure  of  600  pounds 
per  square  inch,  with  an  auxiliary  reservoir  from  which  the 
motors  are  operated  at  not  more  than  140  pounds  pressure. 
This   style   of  compressed-air   locomotive    is    made    in    twelve 


Fig.  421.— industrial  pneumatic  locomotive. 

sizes,   the  smallest  having  motor  cylinders  4x8   inches ;    the 
largest,  11x14  inches. 

The  larger  locomotives  built  for  the  longer  runs  required 
on  plantations  and  for  shipping  heavy  goods  from  iron  works 
and  factories  are  also  made  in  twelve  sizes  with  air-storage  ca- 
pacity of  from  45  to  260  cubic  feet  of  compressed  air  at  from 
600  to  700  pounds  pressure. 


COMPRESSED   AIR    IN    RAILWAY    SERVICE. 


593 


COMPRESSED    AIR    IN    RAILWAY    SIGNALLING. 

Automatic  apparatus  operated  by  compressed  air  for  ringing 
bells  at  highway  crossings  are  in  practical  operation.  In  Fig. 
422  is  shown  an  elevation  and  plan  of  the  apparatus  of  the 
Lyman  Pneumatic  Signal  Company  of  New  York. 

A  small  air-compressing  cylinder  is  located  near  the  rail  and 
operated  by  a  lever  which 
is  depressed  by  the  wheels 
of  a  passing  train,  send- 
ing an  air  impulse 
through  an  underground 
pipe  to  a  distant  crossing 
which  makes  an  electric 
contact  that  rings  a  bell. 
A  is  the  lever,  i)  a  slotted 
cam  on  a  rocking  shaft 
B.  A  train  coming  in 
one  direction  swings  the 
lever  and  cam  shaft  and 
lifts  the  plate  C  and  the 
connected  air  piston.  A  train  from  the  opposite  direction  only 
depresses  the  lever  in  the  cam  slot  and  does  not  give  the  air  im- 
pulse to  the  signal  bell. 

The  shortest  train  repeats  the  air  impulses  and  furnishes 
sufficient  power  to  close  the  bell  circuit  for  the  required  time 
for  signalling.  Fig.  423  shows  the  method  of  arranging  the 
position  of  the  air  apparatus  to  the  north  or  south  of  a  crossing. 

The  central  compressor  C  is  to  open  the  bell  circuit  and  stops 

the  ringing  by  making  an   air  impulse  on  the  piston  C  (Fig. 

424).     Its  location  should  be  at  the  track  opposite  the  signal 

bell.     In  operation  an  impulse  of  air  coming  through  u  (Fig.  424) 

lifts  the  piston  in  A^and,  by  means  of  rod  3,  closes  the  electric 

circuit  which  rings  the  bell.     The   bell  rings  as  long  as  the 
38 


Fig.  422.— signal  air  compressor. 


594 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


piston  of  iV  remains  up,  and  this  time  is  governed  not  only  by 
the  length  of  the  train  that  sends  the  air  impulse,  but  also  by  the 
fit  of  the  piston  and  the  size  of  the  air  escape,  which  can  be 
adjusted  for  any  desired  length  of  time.  When  the  piston  in 
C  (Fig.  423)  is  lifted  it  forces  air  into  the  upper  ends  of  A^and 
S  (Fig.  424)  and  at  the  same  time  lifts  pins  i  and  2,  by  which 
valves  a  and  d  are  opened,  exhausting  the  pressure  in  the  lower 


A 


_n 


Fig.  423.— the  signal  station. 


ends  of  the  upper  cylinders.  The  reference  letters  N,  C,  and 
5  in  (Fig.  424)  have  the  same  general  meaning  as  the  same  let- 
ters in  Fig.  423. 

A  pneumatic  railway  switch  and  signal  system  has  been  de- 
vised and  put  in  experimental  operation,  by  which  the  switches 
and  signals  are  operated  from  a  distant  station  by  means  of 
compressed  air  generated  by  hand  power  in  the  switch  station 
in  sufficient  quantity  to  operate  the  local  switch  and  signal 
plant.  The  system  is  operated  by  a  double  pipe  line  with  slide- 
valve  connections  operated  by  levers  in  the  signal  tower,  which 
by  air  pressure  of  about  80  pounds  operate  pistons  in  cylinders 
at  the  switches  and  signal  poles,  and  thus  throw  a  switch  or 
signal  to  its  proper  position.  The  system  is  very  complex  in 
its  details,  which  prevents  an  intelligent  illustration  here.  It 
is  in  use  on  the  New  Jersey  Central  and  other  railways. 


COMPRESSED   AIR   IN    RAILWAY    SERVICE. 


595 


THE   INTERLOCKING    SIGNAL   AND    SWITCH    SYSTEM. 


After  eighteen  years  of  costly  and  extensive  experimenting, 
the  pneumatic  interlocking  signal  and  switch  system  has  been 
made  a  success  and  a  fixture  at  the  leading  terminal  stations  in 
this  country.  By  its  aid  one  man  now  does  the  work  that 
would  otherwise  require  the  combined  efforts  of  six  operators, 
and  he  does  the  work  better,  the  chances  for  his  making  mis- 
takes having  been  reduced  to  a  minimum.  With  the  lever  in 
hand  he  controls  the  marvellously  efficient  interlocking  machine, 
which  in  turn  controls  a  number  of 
switches  and  signals  connected  by 
pneumatic  cylinders.  As  many  as  a 
dozen  trains  may  be  rushing  down 
on  the  signal-house ;  one  movement 
of  his  hand — and  he  has  signalled 
them  all;  another  movement — and  he 
has  steered  each  individual  train  across 
a  switch,  launching  it  on  its  proper 
course.  The  system  in  use  at  the 
Boston  Southern  station  is  the  largest 
known.  There  are  no  less  than  two 
hundred  and  thirty-eight  pneumatic 
switches  in  operation;  eleven  trains 
may  move  simultaneously  into  or  out 
of  the  train-shed;  one  hundred  and 
forty-eight  semaphore  signals  are  pro- 
vided for  the  four  hundred  possible  routes  presented  in  the 
switch  system  of  that  terminal. 


Fig. 


AIR  PISTONS  UNDER  THE 
SIGNAL  BELL. 


THE    PNEUMATIC    BAGGAGE-HANDLER. 


The  Grand  Rapids  &.  Indiana  Railroad  has  gone  one  step 
farther  by  lately  adopting  the  pneumatic  "  baggage-handler " 
system.     This  device  has  proved  itself  able  to  handle  heavy 


596 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


baggage  much  more  rapidly  than  it  could  otherwise  be  handled, 
and,  moreover,  to  do  away  with  breakage.  The  day  of  the 
baggage-smasher  may,  therefore,  be  past.  The  machine  is  a 
very  simple  arrangement  of  air  cylinder  and  baggage  support. 
The  latter  is  lowered  to  the  platform,  where  it  receives  the  bag- 
gage. Then  it  rises  quickly  and  is  automatically 
swung  around  by  a  cam  action,  carrying  the  bag- 
gage into  the  car.  The  lift  is  operated  by  air 
drawn  from  the  train  tanks  to  a  special  reser- 
voir, and  it  is  controlled  by  the  baggageman 
through  suitable  cocks  on  the  inside  of  the  car. 
The  machine  has  a  lifting  capacity  of  500  pounds, 
with  70  pounds  of  air  pressure ;    it  has  a  spring- 


FlG.    425.— THE   PNEUMATIC   RAILWAY  GATE. 

scale  device  providing  for  the  weighing  of  the  baggage  as  it  is 
handled,  and  it  is  able  to  load  trunks  at  the  rate  of  six  pieces 
every  thirty-two  seconds.  For  country  stations  where  now 
there  is  only  one  man  to  handle  the  baggage,  with  the  usual  dis- 
astrous results,  this  device  will  save  many  a  trunk  from  being 
damaged  or  smashed. 


THE    PNEUMATIC    RAILWAY    GATE. 

Among  the  many  applications  of  compressed  air  for  operat- 
ing special  appliances  on  railway  lines  is  the  pneumatic  rail- 
way gate.  By  this  appliance  the  man  in  the  signal-tower  with 
a  small  hand  air-compressor  pumps  up  a  pressure  sufficient  for 
operating  the  gates,  to  which  the  air  is  transmitted  for  a  consid- 
erable distance  by  a  double-pipe  connection  with  each  gate  to 
supply  compressed  air  to  each  side  of  a  piston,  to  the  rod  of 
which  is  attached  a  chain  running  over  a  sheave  and  up  over 


COMPRESSED   AIR    IN    RAILWAY    SERVICE.  597 

a  sector  to  which  the  gate  bars  are  attached.  A  diaphragm 
piston  takes  air  by  a  second  pipe  line  to  lock  the  gate  at  open 
and  closed  position.  The  gate  is  balanced  so  that  the  effort  of 
opening  and  closing  the  gates  is  very  small,  and  a  number  of 
gates  may  be  operated  at  the  same  time.  About  forty  railways 
in  the  United  States  are  now  operating  this  system.  They 
are  built  by  the  Boque  &  Mills  Manufacturing  Company,  Chi- 
cago, 111. 

THE    PNEUMATIC    DUMPING-CAR. 

One  of  the  later  improvements  in  railway-car  construction 
is  the  compressed-air  dumping-car,  made  by  the  Thatcher  Car 
and  Construction  Company,  New  York  City.  The  body  of  the 
car  being  pivoted  centrally  will  dump  to  either  side,  or  to  one 
side  only,  according  to  its  construction.  This  is  done  by  means 
of  a  cylinder  mounted  on  the  truck  frame,  the  piston  of  which 
is  coupled  direct  to  the  car  body;  another  small  cylinder  called 
the  "latch  cylinder,"  fitted  with  piston  rod  and  slide  valve, 
positively  and  automatically  operates 
the  latches  which  lock  the  car  body 
in  its  horizontal  position,  and  also 
regulates  the  air  pressure  to  the 
large  or  dumping  cylinder  as  re- 
quired, moving  its  piston  up  and 
down,  thus  dumping  the  load  and 
returning  the  body  to  its  horizontal 
position  and  locking  it.      An   inde-     fig.    426.-THE  pneumatic  dump- 

-  ,  .  1    .     1  1  ING-CAR. 

pendent  reservoir  which  each  car  car- 
ries contains  an  ample  supply  of  air  for  operating  the  dumping 
cylinder,  and  is  charged  by  the  engineer  through  a  train  pipe 
used  for  the  air  brakes  at  times  when  the  air  brake  is  not  in 
use.  The  pressure  is  held  in  the  receiver  by  a  check  valve,  so 
that  the  action  of  the  air  brakes  is  not  interfered  with. 


598  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

THE    PNEUMATIC    TELEGRAPH. 

For  local  purposes  and  short  distances,  so  as  to  connect  dif- 
ferent parts  of  buildings,  factories,  etc.,  the  pneumatic  or  air- 
pressure  telegraph  has  of  late  been  successfully  introduced. 
The  pneumatic  telegraph  is  operated  by  compressing  a  quantity 
of  air  in  a  rubber  receptacle  and  forcing  the  same  through  the 
connecting  pipes  to  act  on  a  second  distant  receptacle  that  is 
held  compressed  when  in  a  state  of  rest.  The  expansion 'of 
this  second  receptacle  actuates  a  bell  or  other  signalling  appa- 
ratus. The  apparatus  is,  however,  not  applicable  to  greater  dis- 
tances, as  the  volume  of  air  in  the  communicating  pipes  is  too 
large  to  be  compressed  with  considerable  power  by  the  pressure 
exerted  by  the  first  receptacle,  especially  as  such  pipe  connec- 
tions cannot  be  kept  tight  enough  to  prevent  the  escape  of  air. 
The  Italian  engineer  Guattari  has  overcome  in  a  simple  and  in- 
genious manner  some  of  the  difficulties  of  these  telegraphs,  by 
substituting,  in  place  of  a  few  powerful  compressions,  a  quick 
succession  of  alternating  compressions  and  dilatations,  which 
produce,  so  to  say,  an  oscillating  motion  of  the  air  in  the  pipes. 

THE   AIR    BRAKE   AND    ITS    WORK. 

The  air  brake  dates  its  practical  inception  from  the  year 
1869,  in  the  "  straight  air  brake"  system  of  George  Westing- 
house,  Jr. 

This  consisted  of  a  pump  operated  by  steam  from  the  loco- 
motive boiler,  which  compressed  air  into  a  reservoir  conveniently 
located  about  the  engine.  This  was  under  the  control  of  the 
engineer  by  means  of  a  valve  in  a  pipe  leading  from  the  reservoir. 
From  this  valve  a  pipe  extended  under  the  tender  and  was 
attached  by  flexible  hose  connections  to  a  similar  pipe  under  the 
entire  length  of  each  car.  Branch  pipes  led  to  "  brake  cylinders, " 
and  the  rods  of  the  pistons  in  the  latter  were  connected  with 
the  brake  levers  on  the  cars.  By  placing  the  brake-valve 
handle  in  such  a  position  that  the  reservoir  on  the  engine  was 


COMPRESSED   AIR    IN    RAILWAY    SERVICE. 


599 


connected  with  the  train  line  under  the  cars,  air  pressure  passed 
to  these  cylinders,  pushing  the  pistons  outward,  operating  the 
brake-levers,  and  forcing  the  brake-shoes  against  the  wheels. 
It  was  found  that  the  operation  of  this  apparatus  was  too  slow, 
dangerous  when  used  on  long  trains,  and  did  not  meet  require- 
ments. 

About  1872  or  1873  Westinghouse  produced  a  "plain  auto- 
matic brake "  which  embodied  the  addition  of  an  auxiliary 
reservoir  and  a  triple  valve  to  each  vehicle.  Each  reservoir  was 
of  a  capacity  sufficient  to  provide  an  amount  of  compressed 
air  to  supply  the  power  for  the  car  on  which  it  was  placed. 


TO   AUXILIARY 


TO  CYLrNDER 


TO   TRAIN    LINE 


Fig.  427.— plain  triple  valve. 
Showing  service  position. 


The  operation  of  this  brake  was  radically  different  from  that  of 
the  "  straight  air  brake."  In  the  former  the  compressed  air  was 
stored  in  the  main  reservoir  until  required  for  the  application 
of  brakes ;  in  the  latter  the  main  and  auxiliary  reservoirs  and 
train  pipe  were  always  charged  with  compressed  air  at  working 
pressure,  to  prevent  the  application  of  the  brakes.  The  former 
system  was  operated  by  pressure  from  the  main  reservoir;  the 
latter  system  was  operated  by  a  reduction  of  pressure  in  the 
train  pipe,  which  reduction  caused  the  triple  valve  automatically 
to  assume  a  position  that  would  permit  the  pressure  stored  in 
the  car  reservoir  to  flow  through  the  triple  valve  into  the  brake 
cylinder.  It  was  automatic  in  action  in  case  of  accident,  such 
as  the  bursting  of  hose  or  the  train  breaking  in  two,  but  like  the 


6oO  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

"straight  air  brake  "  was  not  found  to  be  capable  of  successful 
operation  on  long  trains  of  freight  cars. 

In  1885  the  Railway  Master  Car-Builders'  Association  ar- 
ranged for  a  series  of  experiments.  Several  companies  entered 
into  the  competition,  but  none  succeeded  in  stopping  long 
trains  of  freight  cars  without  violent  and  disastrous  shocks. 
The  trials  were  renewed  in  1887,  with  five  competing  com- 
panies. The  report  of  the  committee  was  against  all  the  com- 
peting devices,  the  committee  concluding  that  air  brakes  actu- 
ated by  electricity  were  the  only  ones  likely  to  be  capable  of 
successful  operation  on  long  trains  of  freight  cars. 

After  these  trials  Mr.  Westinghouse  set  himself  to  work  to 
obviate  the  difficulties  that  had  not  yet  been  overcome,  namely, 
to  provide  for  practically  instantaneous  application  of  the  brakes 
throughout  a  train,  and  to  prevent  shocks  to  the  cars. 

In  the  latter  part  of  1887  he  succeeded  in  constructing  a 
quick-action  automatic  brake,  capable  of  being  successfully  ap- 
plied to  a  train  of  fifty  or  more  cars,  and  operative  under  all  con- 
ditions of  practical  railway  service.  The  requirements  with 
which  he  then  for  the  first  time  successfully  complied  were:  i. 
The  regulation  of  the  force  to  be  applied  to  the  brake-shoes  so  as 
to  secure  all  necessary  graduations,  from  the  mere  slackening  of 
speed  to  the  service-stop,  and  from  the  service-stop  to  the 
emergency-stop.  2.  The  automatic  operation  of  the  brakes  in 
case  of  accident.  3.  The  practically  simultaneous  operation  of 
the  brakes  on  each  car,  so  that,  in  long  trains  of  freight  cars, 
shocks  might  be  avoided.  4.  The  control  of  all  these  opera- 
tions by  the  engineer.  5.  Certainty  of  operation  under  all  con- 
ditions. This  was  found  to  be  the  first  system  which  practi- 
cally solved  the  problem  of  quickly  stopping  a  long  freight  train 
in  time  of  danger,  and,  if  desired,  also  permitted  of  a  gradual 
application. 

Plate  A  illustrates  the  relation  and  general  management  of 
the  parts  of  the  air-brake  equipment  on  an  engine,  tender,  and 
passenger  car.     The  tender  equipment  shows  the  "  plain  triple  " 


COMPRESSED    AIR    IN    RAILWAY    SERVICE. 


60 1 


valve  used  on  engines  and  tenders,  while  the  triple  valve  shown 
on  the  car  equipment  is  the  ''quick-action"  type.  The  main 
reservoir  is  carried  beneath  the  engine  and  is  charged  with  air 
from  a  pump  also  on  the  engine,  the  pump  being  operated 
by  steam  from  the  boiler.  The  "engineer's  brake  and  equaliz- 
ing discharge  valve  "  is  located  in  the  cab  of  the  engine  and  is 
connected  to  a  pipe  leading  from  the  main  reservoir  and  a  second 
pipe  communicating  with  the  train  pipe.  This  valve,  under  the 
control  of  the  engineer,  regulates  the  flow  of  air  from  the  main 


< TO  AO^TLT/fRy 


< TO  CYLl.NDJEB 


Fig.  428.— quick-action  triple  valve. 
Showing  release  position. 

reservoir  into  the  train  pipe  for  releasing  the  brakes,  and  charg- 
ing the  auxiliary  reservoirs,  and  from  the  train  or  brake  pipe  to 
the  atmosphere  for  applying  the  brakes.  The  train  pipe  leads 
beneath  all  the  cars  of  a  train,  being  connected  between  the 
cars  by  flexible  hose  coupled  to  the  pipe  sections.  By  means 
of  an  angle-cock  at  each  end  of  the  pipe  of  each  car,  such  pipe  is 
closed  before  separating  the  couplings,  thus  preventing  the  es- 
cape of  air  and  the  application  of  the  brakes  when  the  cars  are 
uncoupled. 

Beneath  each  car  is  an  auxiliary  reservoir  which  takes  a 
supply  of  air  from  the  main  reservoir,  through  the  train  pipe. 


602 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


and  stores  it  for  use  on  its  own  car.  The  brake  cylinder,  by 
a  suitable  pipe,  is  connected  to  the  triple  valve,  and  its  piston 
rod  is  attached  to  the  brake  levers  in  such  a  manner  that,  when 
the  piston  is  forced  out  by  the  air  pressure,  the  brakes  are  applied. 
The  "quick-action"  automatic  triple  valve  is  connected  to  the 


Fig.  429.— quick-action  triple  valve. 
Showing  release  position. 

main  train  pipe,  auxiliary  reservoir,  and  brake  cylinder,  and 
as  its  name  implies,  it,  in  response  to  variations  of  train-pipe 
pressure,  performs  three  functions  in  the  operation  of  the 
brake:  applies  the  brake,  releases  it,  and  charges  the  auxiliary 
reservoir.  When  a  reduction  of  air  pressure  is  made  in  the 
train    pipe,    the    auxiliary    reservoir   pressure,    which    is    then 


COMPRESSED    AIR   IN    RAILWAY    SERVICE.  603 

greater,  forces  the  triple  piston,  and  it  in  turn  moves  the  slide 
valve,  to  a  position  such  that  a  port  connection  is  made  permit- 
ting air  to  flow  from  the  auxiliary  reservoir  to  the  brake  cylin- 
der. If  when  the  brake  is  applied  the  engineer  permits  press- 
ure from  the  main  reservoir  on  the  engine  to  enter  the  train 
pipe,  its  pressure  is  raised  to  an  amount  in  excess  of  that  in 
the  auxiliary  reservoir.  With  the  train-pipe  pressure  greater 
than  that  in  the  auxiliary  reservoir,  the  triple  piston  and  slide 
valve  are  forced  back  to  what  is  known  as  release  position,  in 
which  position  a  port  in  the  slide  valve  permits  brake-cylinder 
pressure  to  escape  to  the  atmosphere,  and  a  small  port,  known 
as  the  feed  port,  connects  the  two  sides  of  the  triple  piston, 
thus  recharging  the  auxiliary  reservoir  from  the  train  pipe  in 
anticipation  of  a  future  use  of  the  brake. 

The  quick-action  triple  differs  from  the  plain  triple  Fig.  427  in 
that  it  has  supplemental  valves  which,  in  case  of  a  sudden  reduc- 
tion, made  by  the  engineer,  by  the  train  parting,  or  otherwise, 
the  brakes  are  not  only  applied  more  quickly,  but  are  applied 
with  greater  force  due  to  the  supplemental  valves  unseating, 
thus  allowing  a  portion  of  the  train-pipe  pressure  to  reach  the 
brake  cylinder.  The  air  taken  from  the  train  pipe  on  the  first 
car  by  the  supplemental  valves,  in  an  emergency  application, 
causes  a  sudden  reduction  which  throws  the  next  triple  into 
quick  action,  this  one  the  next,  and  so  on  throughout  the  train, 
the  brakes  applying  with  such  rapidity  that,  with  a  fifty-car 
train,  the  fiftieth  brake  will  start  to  apply  inside  of  two  and 
one-half  seconds. 

PARTS    IN    THE    FOLDING    PLATE,   A. 

Auxiliary  Reservoir. — A  reservoir,  one  of  which  is  located 
under  each  vehicle,  in  which  air  is  stored  for  the  purpose  of 
furnishing  braking  power  for  the  vehicle  upon  which  it  is 
located. 

Brake  Cylinder. — That  part  of  the  brake  system  in  which 
the  piston,  actuated  by  compressed  air  when  the  brake  is  ap- 


604  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

plied,  is  located.  The  piston,  acting  upon  a  system  of  levers, 
draws  the  brake  shoes  against  the  wheels,  thus  producing  the 
retarding  power  which  tends  to  stop  the  rotation  of  the  wheels. 

Triple  Valve. — A  valve,  one  of  which  is  located  upon 
each  vehicle  equipped  with  an  air  brake.  It  derives  its  name 
from  the  three  functions  it  automatically  performs  in  response 
to  variations  of  train  pipe  and  auxiliary  reservoir  pressures; 
it  automatically  charges  the  auxiliar}^  reservoir,  applies,  and 
releases  the  brake. 

Stop-Cock. — A  valve  by  means  of  which  the  brake  on  any 
vehicle  may  be  cut  in  or  out.  With  each  equipment,  it  is  found 
in  the  pipe  which  connects  the  main  train  pipe  with  the  triple 
valve. 

Car  Drain  Cup. — A  cast-iron  cup  in  which  is  placed  a 
piece  of  perforated  brass ;  it  acts  as  a  strainer  to  prohibit  the 
passage  of  any  foreign  substance  from  the  main  train  pipe  into 
the  triple  valve. 

Angle  Cock. — A  valve,  one  of  which  is  located  at  either 
end  of  every  vehicle.  The  handle  may  be  turned  so  that  the 
valve  will  permit  air  to  pass  through  into  the  train  pipe  beyond, 
or  so  as  to  stop  the  flow  of  air  by  the  point  at  which  it  is  located. 

Hose. — A  flexible  connection  which,  with  the  cast-iron 
coupling,  furnishes  a  means  of  connecting  the  train  pipe  on  one 
vehicle  with  that  on  the  adjoining  one.  In  case  the  train  pulls 
apart  the  couplings  separate,  thus  permitting  of  a  discharge  of 
air  from  the  train  pipe  which  causes  the  brakes  to  apply. 

Conductor's  Valve. — A  valve  having  a  pipe  connection  to 
the  main  train  pipe,  and  so  located  in  baggage,  mail,  and  pas- 
senger cars  that  it  is  easily  accessible  to  the  occupants ;  by  turn- 
ing the  handle  of  the  valve  a  sudden  discharge  of  air  is  made 
from  the  train  pipe,  thus  causing  a  rapid  application  of  the 
brakes  throughout  the  train. 

Engineer's  Brake  Valve. — A  valve,  located  within  con- 
venient reach  of  the  engineer,  by  means  of  which  he  is  enabled 
to  control  the  amount  of  train-pipe  pressure  carried,  the  ap- 


COMPRESSED    AIR    IN    RAILWAY    SERVICE.  605 

plication  and  release  of  the  brakes,  also  the  recharging  of  the 
brake  system. 

Brake-Valve  Reservoir. — Usually  located  beneath  the 
cab  foot-boards,  it  furnishes  a  considerable  volume  of  air  above 
the  equalizing  piston  of  the  brake  valve ;  this  volume  permits 
the  engineer  to  make  a  gradual  reduction  of  pressure  above  the 
piston,  in  response  to  which  it  rises  gradually,  thus  allowing 
train-pipe  pressure  to  escape  at  the  "train  line  exhaust,"  com- 
paratively slowly.  A  slow  reduction  causes  a  gradual  application 
of  the  brakes,  as  in  station  stops;  a  quick  reduction  causes  a 
quick  application  of  the  brakes,  such  as  is  used  in  cases  of  im- 
minent danger. 

Pump  Governor. — The  part  shown  just  to  the  left  of  the 
pump.  It  is  designed  to  shut  off  the  steam  supply  to  the  pump 
when  a  predetermined  air  pressure  has  been  obtained. 

Air  Pump. — It  is  shown  at  the  extreme  right  of  Plate  A. 
The  top  or  steam  piston  actuates  the  lower  or  air  piston,  which 
latter  compresses  air  on  one  side,  while  on  the  other,  air  at 
atmospheric  pressure  is  being  drawn  in.  The  air  compressed 
lifts  one  of  the  discharge  valves  and  passes  on  to  the  main 
reservoir,  from  which  point  it  passes  through  the  brake  valve 
into  the  brake  system  at  the  discretion  of  the  engineer. 

Main  Reservoir. — The  one  usually  placed  upon  the  en- 
gine, in  which  a  large  supply  of  air  is  stored  for  the  purpose  of 
releasing  the  brakes  and  recharging  the  brake  system  when  so 
desired.  Air  for  the  signal  system  is  also  taken  from  the  main 
reservoir. 

Westinghouse  Air-Signal  Equipment. 

The  compressed-air  train  air-signalling  apparatus  has  be- 
come one  of  the  indispensable  conveniences  in  passenger  rail- 
way service. 

It  consists  of  a  pipe  extending  from  the  main  reservoir  on 
the  engine  to  a  reducing  valve  (Fig.  430)  which  reduces  the 
main  reservoir  pressure  to  40  pounds,   the  amount  used  in  the 


6o6 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


signal  system.  From  the  reducing  valve  the  air  flows  to  a  tee, 
one  branch  of  which  leads  to  the  signal  valve  (Fig.  431),  and 
the  other  to  a  separate  pipe  which  passes  back  to  the  end  of 
the  train.  On  each  car  is  placed  a  discharge  valve  to  which  a 
cord,  running  the  full  length  of  each  car,  is  attached. 

The  pressure  in  chambers  A  and  B  (Fig.  431)  equalizes,  be- 
ing connected  by  a  slightly  loose  fit  of  stem  10  in  bushing  9. 
In  response  to  the  reduction  of  signal-line  pressure,  made  when 
the   discharge  valve   on    a   car   is  opened,   a   reduction  wave 


Fig.  430.- signal  reducing  valve. 

is  carried  to  the  signal  valve,  where  it  first  manifests  itself  in 
chamber  A.  The  greater  pressure  in  chamber  B  raises  the 
diaphragm  12  and  stem  10,  thus  unseating  the  valve  at  the  end 
of  stem  10,  and  air  escapes  at  X  through  a  pipe  leading  to  a 
small  whistle,  located  conveniently  close  to  the  engineer,  caus- 
ing it  to  blow. 

This  same  reduction  wave  causes  the  reducing  valve  to  open, 
and  the  air  from  the  main  reservoir  entering  the  signal  line 
causes  the  pressure  in  chamber  A   (Fig.  431)  to  increase  and 


COMPRESSED   AIR   IN    RAILWAY    SERVICE. 


607 


force  the  diaphragm  down  again,  closing  the  valve  at  the  end 
of  stem  10.  It  is  then  only  necessary  to  wait  two  or  three 
seconds  to  allow  the  pressure  to  equalize  throughout  the  signal 
system,  when  another  signal  may  be  given. 


AIR    BRAKES    FOR   TROLLEY    CARS. 

Compressed  air  is  largely  in  use  for  air  brakes  on  trolley 
and  cable  cars,  the  air  being  compressed  by  direct  connection 
from  the  piston  to  a  cam  on  the  axle,  by  a  reducing  gear  from 


TOSIQNAL  PIPE 


X    >i.  TO  WHISTLE 

Fig.  431.- signal  valve. 

the  axle,  or  by  an  electric  motor  when  available.  This  system 
has  been  placed  on  many  of  the  trolley  roads  in  the  United 
States  and  in  Europe  by  the  Standard  Air  Brake  Company  of 
New  York. 

In  operating  brake  mechanism  by  compressed  air  obtained 
through  the  action  of  their  air-compressor  operated  from  the  axle 
of  the  car,  it  is  necessary  to  stop  the  compressor's  action  when  the 
air  has  been  compressed  to  a  predetermined  limit,  in  order  that 
the  compressor  may  continue  to  run  with  the  axle  but  without 
absorbing  power.  This  is  accomplished  as  follows:  as  long  as 
the  air  has  not  reached  the  set  pressure  to  be  carried,  the  com- 


6o8  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

pressor  forces  air  through  the  discharge  valve  direct  to  the 
reservoir,  and  will  continue  so  to  do  until  the  required  pressure 
is  reached.  The  pressure  will  then  open  a  regulator  valve  and 
admit  air  under  a  diaphragm,  forcing  upward  the  governing 
piston  and  lifting  the  suction  valve  from  its  seat. 

This  allows  the  compressor  piston  to  move  freely,  and  pre- 
vents it  from  doing  any  work  until,  by  application  of  the  air  to 
a  brake-cylinder,  the  pressure  is  reduced. 

The  reduction  of  pressure,  acting  upon  the  regulator,  re- 
leases the  air  confined  under  the  diaphragm,  and  allows  the 
governing  piston  to  fall,  reseats  the  valve,  and  the  compressor 
resumes  furnishing  pressure. 

In  making  a  stop,  only  two  or  three  pounds  of  registered  air 
pressure  is  required.  This  the  compressor  furnishes  in  a  very 
short  travel  of  car.  The  reservoirs  hold  in  reserve  several 
times  the  amount  of  air  required  to  stop  the  car,  even  without 
additional  supply.  The  air  pressure  is  thus  practically  inex- 
haustible under  the  conditions  of  operation. 

When  the  direct  or  geared  axle-driven  compressor  is  used, 
enough  compressed  air  is  automatically  maintained  in  the  reser- 
voir to  admit  of  frequent  stops. 

The  electric  compressor  does  not  depend  upon  the  car  axle; 
it  is  entirely  disconnected  therefrom.  The  motor  is  operated 
by  the  trolley  current  only  when  necessary  to  maintain  proper 
pressure  in  the  storage  reservoir.  All  the  working  parts  of 
these  compressors  are  enclosed.  It  is  only  necessary  to  lubri- 
cate regularly.  The  construction  resembles  that  of  the  modern 
enclosed  motor  in  that  slush,  water,  and  dirt  are  excluded. 

The  electric  compressor  acts  substantially  similar  to  the 
other,  in  so  far  as  relates  to  the  regulating  of  reservoir  press- 
ure. The  automatic  current  controller,  however,  puts  the  elec- 
tric compressor  in  or  out  of  service,  according  as  the  air  supply 
in  the  reservoir  increases  or  diminishes. 

The  electric  compressor  may  be  placed  anywhere  on  a  car, 
under,  inside,  or  outside. 


COMPRESSED    AIR   IN    RAILWAY    SERVICE. 


609 


THE    LOCOMOTIVE    BELL-RINGER. 

If  you  wish  to  hear  locomotive  bells  rung  by  compressed  air, 
you  must  take  a  train  on  the  Kansas  City,  St.  Joseph  &  Council 
Bluffs  Railway,  on  which  line  a  number  of  pneumatic  bell- 
ringers  are  in  operation,  giving  admirable  results. 


Fig.    432.— PNKUMATiC   BELL-RIXGER. 


It  is  attached  to  the  air-pump  receiver  on  a  locomotive,  and 
by  the  automatic  vibration  of  the  air  piston  it  operates  the  bell 
crank  and  rin^s  the  bell. 


Chapter  XXVII. 


PNEUMATIC    WORK 


PNEUMATIC    WORK. 


PNEUMATIC    SHEEP-SHEARING. 

Many  attempts  to  perfect  a  mechanical  device  which  would 
lighten  the  work  for  the  shearer,  prevent  the  wool  from  being 
injured  by  second  cuts,  and  guarantee  the  next  fleece  to  be  even 
in  length,  or  "wool-topped," 
have  in  the  past  twenty  years 
been  made.     But  it  was  only 
when  the  "  Australian  Shear- 
er "  made  its  appearance  that 
the  wool-growers  and   shear- 
ers   gave    the  hand-shearing 
entirely  up. 

In  Fig.  433  is  represented 
an     English     compressed-air 

sheep-shearing  machine.  A  small  piston  vibrates  and  operates 
the  cutters  through  a  lever  with  a  diagonal  slot  in  which  a  pin 
in  the  piston-rod  head  slides.  An  arm  on  the  piston  rod  operates 
the  valves  at  the  end  of  each  stroke. 

The  Australian  sheep-shearing  machine  (Fig.  434)  is  exceed- 
ingly simple,  direct-acting,  and  easy  to  handle.     It  is  composed 


Fig.  433.— sheep-shearer. 


Fig.    434.— AUSTRALIAN   SHEEP-SHEARER. 


of  eight  pieces :    The  body  of  the  shearer,  the  oscillating  fork, 
the  piston,  the  valve,  the  comb,  the  cutter,  the  piston  covers, 


6l4  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

and  the  tightening  ratchet.  The  valve  is  entirely  balanced. 
The  motion  of  the  machine,  similar  to  that  of  a  rock  drill,  is 
given  by  the  piston,  which  is  if-inch  diameter,  -|-inch  stroke. 
The  fork  is  centred  on  a  half-round  bearing,  the  cup  of  which 
forms  an  oil  receptacle,  so  that  the  bearing  is  all  the  time 
working  in  a  bath  of  oil,  reducing  the  friction.  The  pressure- 
nut,  which  regulates  the  pressure  of  the  cutter  on  the  comb,  is 
inside  of  the  body  of  the  machine,  so  that  it  cannot  interfere 
with  or  tear  the  fleece  during  work.  The  machine  having  no 
perceptible  vibration,  as  can  be  proved  by  laying  it  down  on 
the  floor  while  running  at  full  speed,  the  w^ist  of  the  operator 
is  not  subjected  to  any  strain.  The  weight  of  the  machine  is  2 
pounds  2  ounces,  and  this  being  counterbalanced,  the  shearer 
has  neither  strain  nor  weight  to  overcome.  The  motive  power 
is  air  under  a  pressure  of  about  40  pounds  to  the  square  inch, 
which  is  conveyed  to  the  machine  through  a  rubber  tube  \  inch 
in  diameter.  Each  machine  uses  1 5  cubic  feet  free  air  per 
minute.  The  absence  of  joints  and  complications  permits  the 
shearer  to  work  in  any  position  he  desires.  The  machine 
makes  6,000  oscillations  per  minute,  but  does  not  run  hot,  as 
the  exhausted  compressed  air  passes  through  the  hollow  casing 
of  the  body  and  escapes  over  the  cutter,  keeping  the  fleece  well 
before  the  points  of  the  comb,  enabling  the  shearer  to  watch 
the  operation,  and  at  the  same  time  keeping  the  machine  cool 
while  in  his  hands. 

The  inconvenience  of  the  heat  and  the  disadvantage  of  the 
friction  which  causes  the  heat  and  increases  the  wear  and  tear, 
involving  cost  of  repairs  and  fear  of  delay  at  shearing  time,  are 
thus  obviated.  The  simplicity  of  the  construction  dispenses 
with  the  necessity  of  skilled  labor  in  setting  up,  adjusting,  or 
running  the  machine. 

The  use  of  this  machine  reduces  the  time  of  shearing  from 
an  average  of  70  sheep  b}^  hand  to  about  100  per  day  of  ten 
hours.  At  Barsham,  in  Australia,  three  men  sheared  334  sheep 
with  this  machine  in  ten  hours, the  third  dav  thev  ever  handled 


PNEUMATIC    WORK.  615 

machines.  Furthermore,  the  "  Australian  Shearer  "  saves  about 
three-quarters  of  a  pound  of  fleece  wool  per  sheep,  a  profit  of 
about  16  cents;  and  as  the  wool  is  worth  i  cent  a  pound  more 
when  cut  in  this  way,  as  it  is  longer  and  more  uniform  in 
length,  than  by  hand  shearing,  this  would,  with  an  average 
yield  per  sheep  of  about  8  pounds  of  wool,  bring  the  total  profit 
by  the  use  of  this  method  up  to 
24  cents  per  sheep. 

Another  point  in  favor  of  this 
machine  is  that  by  its  use  the 
animals  are  never  mutilated. 

They  are  made  by  Rochet  & 
Company,  Paris,  France. 

COMPRESSED    AIR    IN  A  SAW-MILL. 

The  power  that  operates  a 
saw-mill,  be  it  steam  or  water,  is 
utilized  for  compressing  air  to 
operate  the  various  saw-mill  ap- 
pliances that  both  steam  and  water  are  unfitted  for,  from  the 
trouble  of  condensing  steam  in  interrupted  use  and  the  liability 
of  water  to  freeze  in  cold  weather.  The  log-flipper  for  roll- 
ing logs  out  of  the  log  slide,  shown  in  Fig.  435,  and  the 
nigger  for  rolling  and  turning  logs  on  the  saw-carriage  (Fig. 
436)  are  some  of  the  new  uses  for  compressed  air.  These  de- 
vices, together  with  a  jump  saw  for  cutting  logs  to  the  proper 
length,  and  a  saw-feed  motor,  all  driven  by  compressed  air,  are 
in  successful  operation  at  the  Engel  Saw-Mill,  Orono,  Me. 


COMPRESSED   AIR    IN    BASKET-MAKING. 

Take  the  work  of  basket-making.  Surely,  no  one  ever  heard 
of  any  of  the  old  machines  turning  out  180  bushel-baskets  per 
hour,  or  1,800  baskets  per  day,  but  a  compressed-air  basket- 
making  machine  is  now  doing  it  at  the  Michigan  Avenue  fac- 


FlG.    435.— LOG   FLIPPER. 


6i6 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


tory,  Traverse  City,  Mich.  The  staves  of  the  baskets  are  fast- 
ened to  the  hoops  by  staples  of  wire  taken  from  the  coil,  joined 
and  driven  by  the  machine.  The  staves  radiate  from  a  centre 
in  a  disc-like  shape.  To  bend  them  into  the  lines  of  the  bas- 
ket form,  four  processes  or  movements  are  made  by  the  ma- 
chine, all  of  which  are  automatic  and  obtained  by  the  medium 

of  compressed  air.  The 
whole  combination  is  very 
simple.  The  air  is  not 
cooled,  and  the  machine 
runs  ten  hours  every 
working  day. 

THE     AIR-BRUSH. 


Then  there  is  the  foun- 
tain  air-brush,  which 
some  claim  will  soon  be 
adopted  by  the  leading 
artists  for  applying  color 
on  canvas.  It  is  shaped 
like  and  is  but  little  lar- 
ger than  a  lead  pencil,  is 
handled  in  the  same  man- 


FlG.    436.— PNEUMAIIC  NIGGER. 


ner,  applies  color  in  large  quantities  in  a  short  time,  and  is 
yet  adjustable  for  the  finest  line  ever  drawn  on  canvas  by  a 
gifted  artist. 


COMPRESSED    AIR    FOR    BLOWING   YACHT  AND  LAUNCH   WHISTLES. 

To  the  water  sportsman  there  is  nothing  more  pleasing  than 
a  well-toned  air-whistle  for  signalling.  The  push  and  draw 
whistle,  at  the  hand  of  the  wheelman,  by  intelligent  manipu- 
lation can  be  made  not  only  to  give  the  ordinary  signals  for 
navigation,  but  can  be  operated  telegraphically  for  other  com- 
munications. 


PNEUMATIC    WORK. 


617 


A  small  air  tank  under  the  forward  deck  may  be  charged 
by  an  air  pump  operated  by  the  propelling  engine,  and  will  store 
air  sufficient  for  operating  the  whistle  when  the  boat  is  not 


Fig.  437.— push  whistle. 


Fig.  438.— pull  whistle. 


running.     They  are  furnished  by  the  Gleason-Peters  Air-Pump 
Company,  New  York  City. 


COMPRESSED    AIR    FOR    BLOWING    FOG    SIGNALS. 

The  United  States  Lighthouse  Department  has  for  some 
time  devoted  much  attention  to  the  improvement  of  its  fog  sig- 
nals, and  to  that  end  has  recently  adopted  compressed  air  in 
place  of  steam  for  sounding  fog  signals.  A  very  compact  plant 
has  been  developed  for  this  ser- 
vice, and  one  is  now  installed 
at  Montauk  Point,  on  the  ex- 
treme eastern  end  of  Long 
Island.  The  motive  power  is 
furnished  by  a  ten-horse-power 
Hornsby-Akro5'd  oil  engine, 
which  drives  an  Ingersoll-Ser- 
geant  Class  E  air  compressor.  The  oil  engine  occupies  a  floor 
space  of  9  feet  2  inches  by  5  feet.  The  air  compressor  has  a  base 
measuring  6  feet  by  2  feet  i  inch,  and  is  capable  of  furnishing 


Fig.   439.— .-MR   TANK   AND  WHISTLE. 


6l8  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

107  cubic  feet  of  free  air  per  minute  at  150  revolutioiivS.  The 
air  is  compressed  and  delivered  to  a  receiver  at  50  pounds  press- 
ure. It  is  then  carried  to  another  receiver  about  200  feet  dis- 
tant. Midway  on  the  pipe  line  a  reducing 
valve  regulates  the  pressure  and  admits  it  to 
the  second  receiver  at  30  pounds  pressure. 
This  receiver  holds  the  immediate  supply  of 
air  to  operate  the  trumpet. 

Exhausting  through  the  siren  at  this  lower 
pressure  enables  the  receiver  to  maintain  the 
supply  after  a  fog  rises  for  a  time  sufficient  to 
get  the  engine  and  compressor  in  operation. 
There  are  two  trumpets  attached  to  the  re- 
ceiver, which  are  used  together  or  alternately, 
as  desired.  A  first-class  siren  is  supposed  to 
consume  12  cubic  feet  of  free  air  per  second. 

The  siren  is  sounded  automatically,  and 
blows  at  intervals  of  30  to  50  seconds.  As  a 
musical  instrument  it  can  be  best  described 
by  calling  it  a  big  clarionet. 

The  Daboll  trumpet  is  another  fog  signal 
similar  in  general  design,  but  having  a  smaller 
range  of  audibility,  and  requiring  less  power. 
The  plant  used  consists  of  a  four  horse-power 
engine  and  a  vertical  belt-driven  compressor 
furnishing  17  to  20  cubic  feet  of  free  air  per 
minute.  It  delivers  air  at  a  pressure  of  from 
5  to  10  pounds  to  a  receiver  which  supplies  the 
trumpet. 

Fig.  440.— siren.  ,~^,        .  /•  •  ^ 

The  importance  of  conveymg  sound  or  a 
signal  to  a  greater  distance  than  heretofore  in  a  fog  or  in  thick 
weather  at  night,  has  long  been  felt,  and  at  last  the  want  has 
been  met  in  the  production  of  the  "  Brown  "  fog-horn  or  siren, 
which  is  illustrated  in  Fig.  440.  It  consists  of  a  chamber  con- 
taining a  peculiar  mechanism  for  producing  a  large  volume  of 


PNEUMATIC    WORK. 


619 


sound  in  the  vibration  of  the  air  passing  the  mechanism,  and 
which  is  still  further  strengthened  by  the  immense  trumpet  that 
surmounts  the  chamber.  It  seems  to  fulfil  all  the  conditions 
required  on  shipboard,  at  lighthouses,  and  on  lightships.  It  has 
been  heard  a  distance  of  31  miles  on  the  open  ocean.  It  re- 
quires about  80  pounds  pressure  for  its  best  work.  When  steam 
is  used,  a  drip  pipe  is  inserted  in  the  chamber  to  drain  off  any 
water  that  may  be  condensed  in  the  apparatus  by  leakage  of 
steam  through  the  valve.  On  the  lightship  off  Sandy  Hook, 
New  York  harbor,  the  air  is  compressed  by  a  kerosene  engine 
and  stored  in  receivers  for  ready  use  in  the  siren. 


COMPRESSED    AIR    FOR    RAISING   SUNKEN    VESSELS. 

The  use  of  air  pumped  beneath  the  sealed  decks  of  sunken 
vessels   for  raising  them   has  been   in   successful   practice  for 

.1  .-____, 


Fig.  441.— the  air-cask  system. 

many  years.  Casks  or  bags  placed  on  the  inside  or  fastened  to 
the  outside,  and  inflated  by  pumping  air  into  them,  has  been 
the  means  of  saving  many  vessels  that  otherwise  would  have 
been  a  total  loss.  Long  iron  tanks  have  been  floated  to  the 
sides  of  a  sunken  vessel  and  filled  with  water  sufficient  to  sink 
them,  when  they  are  attached  to  the  side  of  the  vessel  and  air 
pumped  in  to  displace  the  water.  The  buoyancy  of  the  air 
tanks  raised  the  vessel  to  or  near  the  surface  for  towage  to  a 
shelter.  By  placing  the  air-bags  under  the  deck,  the  schooner 
Glciwla  was  raised  in  Great  South  Bay,  also  a  vessel  in   Puget 


62  o 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Sound.  Failures  have  been  made  by  filling  the  bags  or  casks 
with  too  much  air,  which  expands  in  rising  from  deep  water 
and  bursts  its  enclosure.  Air  vents  at  the  bottom  of  each  bag 
or  cask  are  safety-valves  for  deep-water  work  by  compressed  air. 
The  bursting  of  the  air  bags  has  been  the  cause  of  failure  in 
the  early  work  of  raising  vessels  by  compressed  air.  Colonel 
Gowan  met  this  difficulty  in  the  attempt  to  raise  the  United 
States  steamer  Missouri  at  Gibraltar  in    1845.     He  tried  it  at 


Fig.  442.— the  air-bag  system. 


Sebastopol,  but  failed  at  first.  A  combination  of  floats  and 
compressed  air  finally  made  a  success  in  raising  nearly  one 
hundred  vessels. 

Fig.  442  represents  Captain  Austin's  plan,  in  which  the  large 
inflatable  canvas  bags,  //,  //,  //,  in  the  cut,  were  rendered  water 
and  air  proof  by  india-rubber  and  strengthened  by  envelopes  of 
netting.  Chains  were  swept  under  the  vessel  and  fastened  to 
horizontal  chains  to  which  the  air  bags  were  lashed.  Air  was 
pumped  in  through  the  air  pipes,  /,  ?',  /,  allowing  for  sufficient 
expansion  of  the  air  as  the  vessel  rose. 

Compressed  air  played  a  most  important  part  in  the  raising 


PNEUMATIC   WORK.  62  1 

and  floating  of  the  steamer  PlymoiitJi  from  the  rocks  in  the  har- 
bor of  Newport,  R.  I.  The  steamer  had  double  hulls  with 
compartments  between  the  hulls,  which  were  ruptured  by  the 
vessel  running  upon  the  rocks,  and  many  of  the  partitions  be- 
tween the  compartments  were  injured  so  as  to  cause  leakage 
into  a  large  portion  of  the  space  between  the  hulls. 

It  was  found  that  the  pontoons  and  derricks  could  not  lift 
the  vessel  sufficiently  to  clear  the  rocks,  and  recourse  was  had 
to  pumping  air  into  the  compartments  by  a  compressor  utilized 
for  the  purpose,  which  forced  the  air  throughout  the  compart- 
ments through  the  drainage-pump  pipes  and  thus  added  about 
400  tons  to  the  lifting  power  of  the  derricks  and  pontoons.  It 
was  found  after  floating  the  steamer  that  the  air  compressor 
was  able  to  keep  her  afloat  without  the  pontoons  and  derricks, 
which  were  then  unshipped  and  the  vessel  was  towed  up  to 
Newport. 

COMPRESSED    AIR    IN    SUBMARINE    EXPLORATION. 

There  is  no  condition  of  the  relation  of  compressed  air  to 
human  vitality  more  delicate  and  important  than  when  a  man 
dressed  in  a  diver's  close-fitting  armor  descends  to  the  bottom 
of  the  sea. 

The  sudden  change  of  atmospheric  effect  upon  his  system 
by  great  pressure  in  descent,  and  its  release  in  ascent,  calls  for 
great  caution  as  to  the  time  required  for  the  change  in  press- 
ure, as  well  as  an  experienced  practice  by  degrees  in  depth, 
combined  with  a  strong  vitality  in  the  person,  before  excessive 
depths  can  be  accomplished  and  work  performed.  The  least 
mishap  may  be  fatal,  yet  there  are  men  who  have  practised  this 
work  for  many  years  without  accident  or  material  deterioration 
in  health. 

The  usual  work  of  the  diver  is  under  100  feet  in  depth; 
seldom  150  feet;  and  the  greatest  depth  that  has  ever  been 
reached  by  a  diver  is  204  feet,  requiring  an  air  pressure  of 
88|-  pounds  to  balance  the  water  pressure. 


62: 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


The  armor  consists  of  a  helmet  to  protect  the  head ;  a  dress, 
of  canvas  and  rubber,  attached  to  the  helmet;  shoes,  with  lead 
soles,  to  keep  the  feet  down  and  the  body  upright;  lead  weights 
to  sink  the  diver  to  the  bottom,  and  to  prevent  his  rising  from 
an  over-pressure  of  air  from  the  air-pump.  A  life  or  signal 
line  is  used  for  lowering  and  raising  the  diver,  and  for  the  trans- 
mission of  signals  between  the  diver  and  his  attendant. 


Fig.  443.— submarine  kxplukaiion. 


The  diver,  being  dressed  in  his  flannels,  is  now  equipped 
with  his  dress ;  the  air-hose  is  screwed  to  the  helmet  and  air- 
pump,  the  pump  started  and  the  headpiece  screwed  on,  and  he 
is  lowered  to  the  bottom,  where  he  can  remain  from  one  to  six 
hours,  according  to  the  depth  of  water,  the  speed  of  the  tide, 
and  the  character  of  the  work. 

The  helmet  is  the  most  important  individual  piece  in  the 


PNEUMATIC    WORK. 


623 


outfit,  for  to  it  is  attached  the  regulating  valve  seen  at  the  right 
side  of  the  helmet  in  Fig.  444,  and  in  reach  of  the  diver's 
hand,  allowing  him  to  adjust  the  escape  of  air  to  suit  the  needs 
of  respiration,  irrespective  of  the  automatic  air  escape. 


Fig.  444.— the  diver  in  armor. 


This  helmet  has  the  latest  improvements  in  the  addition  of 
the  top  glass  that  the  diver  may  look  upward  without  throwing 
the  body  back.  A  telephone  attached  to  the  helmet  is  a  late 
and  important  addition  to  the  facilities  for  operating  in  sub- 


624 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


marine  work,  A  transmitter  and  receiver  are  fixed  on  the  inside 
of  the  helmet  and  connected  by  insulated  wires  with  their  coun- 
terpart in  the  hands  of  the  attendant,  by  which  orders  and  in- 
formation may  be  quickly  passed,  which  has  been  a  most  tedi- 
ous process  under  the  old  jerk-cord  system. 

The  amount  of  free  air  required  by  a  diver  varies  somewhat 
under  the  varying  pressure  in  which  he  is  operating  and  of 
habit  in  respiration.     And  as  a  man  in  normal  condition  makes 

about  1 6  respirations  per 
minute  with  an  average  of 
40  cubic  inches  at  each 
respiration,  it  will  require 
nearly  half  a  cubic  foot  of 
free  air  per  minute  for 
respiration  alone,  and  for 
exhausting  the  vapors  from 
the  body  as  much  more, 
or,  say,  a  cubic  foot  per 
minute. 

In  Fig.  446  is  illustrated 
a  submarine  air-pump, 
double-acting,  single  cylin- 
der, of  capacity  for  one 
diver  at  ordinary  depths,  and  to  100  feet  water  pressure.  It  is 
furnished  with  a  water  cistern  for  cooling  the  compressed  air, 
and  a  pressure  gauge. 

The  above  submarine  apparatus  is  manufactured  by  A.  J. 
Morse  &  Son,  Boston,  Mass.  Their  catalogue  contains  inter- 
esting details  in  regard  to  management  in  the  use  of  submarine 
armor,  habits  and  living  of  divers,  and  their  health. 


Fig.  445— the  helmet. 


COMPRESSED    AIR    FOR    DREDGING    CHANNELS. 

Dredging  experiments  have  been  made,  especially  in  Eng- 
land, Holland,  and  the  United  States,  with  apparatus  designed 
for  digging  up  alluvium,  dissolving  in  water  the  materials  of 


PNEUMATIC   WORK. 


625 


which  it  consists,  and  giving  these  up  to  natural  currents  when 
the  latter  have  their  greatest  strength.  Such  experiments, 
however,  have  not  given  satisfactory  results,  since  the  materials 
thus  dredged  were  lifted  but  to  a  small  distance  from  the  bot- 
tom from  which  they  had  been  extracted,  and  thus  almost  im- 
mediately settled  back  again  in  the  same  place.     Although  this 


Fig.  446.— single-cylinder  double-acting  air  pump. 

•  Qode  of  dredging  had  therefore  to  be  given  up,  it  has  been  suc- 
cessfully taken  up  by  Mr.  Meinesz,  who  employs  compressed 
air  for  forcing  to  the  surface  the  material  that  has  been  de- 
tached by  means  of  a  kind  of  harrow,  in  order  to  put  it  thus  in 
contact  with  as  great  a  number  of  molecules  of  water  as  possi- 
ble and  to  give  it  a  velocity  in  a  direction  opposite  that  of  grav- 
40 


626  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

ity.  Once  raised  to  the  surface  of  the  water,  the  sands  are 
carried  off  by  the  current  to  distances  which  vary  according  to 
the  swiftness  of  the  current  and  to  the  depth  from  which  they 
have  been  dredged.  The  whole  question,  then,  resolves  itself 
into  a  study  of  the  direction  and  force  of  the  current,  so  that 
the  deposits  shall  be  borne  away  as  far  as  possible  from  the 
channel  that  it  is  desired  to  excavate. 

A  late  innovation  upon  the  old  system  of  operating  the 
clam-shell  bucket  by  chains,  has  been  made  by  substituting  a 
cylinder  and  piston  moved  by  compressed  air  for  opening  and 
closing  the  bucket;  the  action  being  wholly  independent  of  the 
hoisting  chains  and  of  the  position  of  the  bucket.  The  hose 
for  operating  the  piston  is  wound  on  a  counterbalanced  reel 
and  is  carried  freely  by  the  movement  of  the  bucket. 

The  advantages  claimed  are  a  wider  scope  to  the  action  of 
the  bucket  and  the  utilization  of  the  full  weight  of  the  bucket 
and  air  cylinder  to  produce  a  full-depth  scoop  of  the  bucket^ 
which  in  the  old  way  was  lessened  by  the  pull  of  the  bucket- 
closing  chain. 


Chapter  XXVIII. 


PNEUMATIC   WORK— Continued 


627 


PNEUMATIC   WORK. 

{Continued.) 
THE    COMPRESSED-AIR   BLAST. 

Ax  interesting  application  of  the  use  of  compressed  air  is 
that  of  the  Fallbrook  Railway  Shops  in  furnishing  a  blast  for  the 
boiler-makers'  forges.  The  driving  rig  was  removed  from  an 
ordinary  portable  forge  (Fig. 
447),  and  the  nozzle  B  was 
screwed  in  the  shell  so  that  the 
air  current  would  impinge  on 
the  vanes  of  the  fan  A.  The 
amount  of  throttle  opening  re- 
quired is  very  small  to  drive 
the  fan  at  a  high  rate  of  speed, 
so  that  it  is  remarkably  eco- 
nomical of  air.  The  blast  fur- 
nished is  almost  an  ideal  one  for  this  purpose,  and  one  capable 
of  the  closest  regulation. 

By  the  device  illustrated  in  Fig.  447  the  compressed  air  sup- 
plies a  blast  of  many  times  its  own  volume,  and  wnth  all  the 
pressure  required. 

The  compressed-air  injector  is  illustrated  in  Fig.  448.  The 
fact  is  well  known  that  the  principle  of  action  of  the  steam  in- 
jector and  ejector  may  be  applied  to  air  for  forcing  a  larger 
volume  at  a  less  pressure  into  a  receiver  for  any  use,  and  espe- 
cially for  ventilation. 

Experiments  have  shown  that  one  volume  of  air  when 
passed  through  a  nozzle  as  at  C  (Fig.  448),  when  the  apparatus 
is  arranged  as  an  injector,  at  a  pressure  of  5  pounds  per  square 
inch,  will  induce  30  volumes  of  free  air  as  measured  by  a 
meter.     Air  under  pressure  will  discharge  through  a  nozzle  of 


Fig.  447.— induced  air  blast. 


630 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


best  form  at  a  velocity  of  about  650  feet  per  second;  it  is  easy 
to  understand  that  free  air  will  be  induced  and  discharged  with 
it  into  a  secondary  receiver.  Such  an  arrangement  is  shown 
in  the  cut  (Fig.  44H),  in  which  B  is  the  receiver,  D  the  induced 
current  nozzle,  A  C  the  compressed-air  nozzle,  E  the  air  cham- 
ber, and  F  2^  light  check  and  free-air  inlet. 

This  air  injector  has  been  tried  with  success,  though  the 
experiments  have  not  gone  far  enough  to  determine  to  what 
extent  it  will  effect  a  saving  in  the  production  of  pneumatic 


Fig.  448.— the  compressed-air  injector. 

power.  It  has  been  found  that  with  a  pressure  of  80  pounds  in 
the  first  receiver,  the  injector  will  work  discharging  and  induc- 
ing free  air  into  a  second  receiver  in  which  is  maintained  a 
pressure  of  60  pounds. 

THE    SAND    BLAST. 

The  energy  contained  in  a  single  flying  grain  of  sand  is 
small,  even  when  travelling  at  a  very  considerable  velocity, 
but  it  is  the  exceedingly  small  area  upon  which  this  is  ex- 
pended that  makes  any  cutting  by  it  possible.  As  an  illustra- 
tion of  the  above  points,  take,  for  instance,  the  case  of  a  sand 
blast  using  sand  of  an  average  of  -g-L  inch  in  diameter  and  pro- 
pelled by  air  of  50  pounds  to  the  square  inch,  cutting  granite. 
Such  a  blast,  under  these  circumstances,  will  cut  granite  rap- 
idly.    Why?     Determining  the  above  factors,  first,  such  sand 


PNEUMATIC    WORK.  63I 

grains  will  weigh  on  an  average  about  0.005  grain  and  will  be 
moving  at  the  point  of  impact  with  the  stone  about  400  feet  per 
second,  and  will  therefore  contain  about  0.00176  foot-pound 
energy.  Now,  this  is  certainly  a  very  small  amount,  but  next 
take  the  area  upon  which  it  is  expended. 

The  area  of  first  impact  can  only  be  estimated  from  the  fol- 
lowing considerations:  If  a  piece  of  smooth,  hard  substance  is 
scratched  with  the  edge  of  crystal,  as,  for  instance,  in  ruling 
diffraction  gratings  and  that  class  of  work,  lines  are  readily 
ruled  at  the  rate  of  .00002  to  the  inch,  and  when  examined 
under  the  microscope  the  lines  are  seen  to  be  narrow  in  com- 
parison to  the  space  separating  them,  being  themselves  proba- 
bly not  more  than  ^tj^o-q-  inch  broad,  and  it  is  upon  a  rectangle 
of  the  length  of  side  equal  to  the  breadth  of  one  of  these  lines 
that  the  first  impact  occurs.  This  is  .000000004  square  inch. 
And  the  above-determined  0.00176  foot  pound  of  energy  dis- 
tributed upon  this  area  is  at  the  rate  of  440,000  foot  pounds 
per  square  inch.  Now,  the  strongest  granite  can  stand  only  a 
quiet  crushing  strain  of  some  1,200  tons  per  square  foot,  or  at 
the  rate  of  some  16,600  pounds  to  the  square  inch.  The  con- 
test between  the  stress  developed  at  the  point  of  impact  and  the 
resistance  of  this  object  struck  is  in  this  case  decided  over- 
whelmingly in  favor  of  the  stress  developed.  The  result  is  that 
the  granite  under  the  point  of  the  first  impact  is  crushed  and 
crumbled  to  dust,  letting  the  grain  of  sand  progress  until  in  its 
advance  it  has  expended  its  energy  and  increased  the  area  of  con- 
tact, when  the  pressure  there  falls  below  the  crushing  strength 
of  the  granite,  and  then  the  action  of  that  grain  is  over  and  it 
rebounds  from  the  stone.  The  striking  edge  or  point  of  the 
grain  of  sand  is  also  crushed,  and  contributes  to  increasing 
the  area  of  contact  between  it  and  the  granite.  The  effect  of  the 
above  sand  blast,  when  striking  a  piece  of  wrought  iron  in  place 
of  the  granite,  will  be  that  the  iron,  instead  of  being  pulverized 
like  the  granite,  is  only  indented.  The  result  is  that  no  metal 
is  removed,  but  a  small  indentation  produced.     Other  grains 


632  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

striking  in  the  immediate  vicinity  of  this  indentation  simply 
shove  the  metal  back  into  it  again  and  obliterate  the  effect  of 
the  first  grain.  Thus  no  effect  is  produced,  but  the  surface  is 
simply  roughened  by  the  indentations  of  the  sand  grains.  This 
is  the  normal  effect  of  the  blast  upon  all  metals.  If  they  are 
exposed  for  a  long  time  to  the  action  of  the  sand,  as  in  a  sand- 
blast machine,  metals  wear  away,  because  the  surface  metal  is 
exhausted  by  the  constant  bending  so  that  it  at  last  breaks.  If 
the  blast  is  directed  upon  a  piece  of  soft  rubber  the  same  action 
as  in  the  case  of  the  metal  takes  place,  but  in  this  case  the  elas- 
ticity of  the  rubber  is  such  as  to  enable  it  to  resume  its  original 
shape  after  the  force  of  the  impact  has  been  expended  in  de- 
forming it,  and  there  is  no  residual  effect  whatever  upon  the 
rubber,  the  grain  of  sand  rebounding  with  almost  its  original 
velocity.  These  three  actions  and  the  combinations  of  them 
explain  all  the  different  effects  of  the  sand  blast,  in  cutting  and 
refusing  to  cut  various  substances. 

In  surface  obscuring  or  ornamenting,  such  as  in  glass  work, 
for  which  the  sand  blast  has  been  more  used  than  for  all  other 
purposes  combined,  the  problem  is  entirely  different.  The 
effect  wanted  is  to  break  the  continuity  of  the  surface  struck, 
and  this  once  obtained  any  further  force  in  the  blow  of  the 
sand  is  wasted,  and  an  exceedingly  great  number  of  light  blows 
is  what  is  desired.  Therefore  a  very  fine  sand  is  used  and  a 
large  quantity  thrown  in  proportion  to  the  propelling  jet,  which 
gives  a  moderate  velocity.  So  important  is  the  adaptation  of 
the  size  of  sand  to  the  work  that  if  two  exactly  similar  machines 
are  taken,  one  using  fine  and  the  other  coarse  sand,  and  both 
using  the  same  pressure  of  air  to  drive  the  sand  and  the  same 
size  jet,  the  machine  using  fine  .sand  will  obscure  three  times 
the  work  that  the  machine  using  coarse  sand  will  do.  But  in 
cutting  or  perforating  glass  or  stone  the  machine  using  coarse 
sand  will  do  three  times  the  work  of  the  machine  using  fine 
sand.  In  one  case  the  blows  are  too  few  to  break  up  much  sur- 
face, and  in  the  other  case  they  are  too  light  to  do  much  cut- 


PNEUMATIC    WORK. 


633 


ting.     Thus,  by  use  of  sand  unsuited  to  the  work,  the  efficiency 
of  a  good  machine  can  be  reduced  over  60  per  cent. 


THE    SAND    BLAST   AND    ITS    WORK. 

The  economy  of  the  sand  blast  to  lighten  the  labor  of  clean- 
ing castings  in  the  foundry  is  a  most  important  use  of  air  apart 
from  the  melting  blast.  With  it,  the  air  hoist,  the  moulding 
machine,  and  the  air  lift,  and  we  may  add  the  air  rammer,  have 
brought  the  work  of  the  foundr}''  to  a  high  degree  of  perfection 
and  economy  in  their  labor-saving  aspects.     On  an  average  it 


Fig.  449.— ward  &  nash  apparatus. 

now  takes  but  one-third  of  the  time  to  clean  a  casting  or  the 
day's  run,  as  was  formerly  the  case  by  hand. 

Neither  files  nor  brushes  can  get  around  recesses,  fins,  and 
risers  as  the  blast  does,  and  when  so  cleaned  the  air-chipping 
hammer  has  a  clean  path  for  work. 

In  Fig.  449  is  illustrated  the  Ward  &  Nash  sand-blast  ap- 
paratus at  work.  The  sand  is  fed  to  the  air  pipe  as  shown  in 
Fig.  450,  and  carried  through  a  short  rubber  hose  and  ejected 
through  a  nozzle  at  great  velocity,  estimated  at  from  350  to 
500  feet  per  second.  At  this  great  velocity  the  sand  has  an 
intense  cutting  power. 

For  small  castings  suitable  for  the  tumbling  barrel,  the  sand 
blast  facilitates  and  preserves  the  sharp  corners  of  castings  to  a 


634 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


marvellous  extent.  The  barrel  used  for  this  work  is  open  at 
both  ends  and  revolves  on  rollers ;  the  sand  blast  enters  at  one 
or  both  ends  of  the  barrel,  while  it  slowly  rolls  the  castings 
over.  In  the  detail  of  the  sand  tank  (Fig.  450)  the  compressed 
air  enters  the  lower  compartment  at  B,  and  issuing  through  the 
cross  pipe  D  receives  its  charge  of  sand  graduated  by  the  slide 
valve  F,  which  is  regulated  by  the  lever  E.  C  C  is  the  conical 
partition  that  holds  the  sand  in  the  upper  chamber.  A  is  the 
inlet  valve  held  in  place  by  a  spring.  The  upper  section  is  the 
hopper  into  which  the  sand  is  dumped,  when  by  pushing  down 

the  spring  with    the  valve  F  closed  the 
sand  drops  into  the  feed  chamber. 

.  For  the  foundry  sand  blast  an  air 
pressure  of  25  pounds  per  square  inch 
seems  to  meet  the  requirement;  but 
where  hoists,  hammer-chipping  tools,  and 
rammers  are  used  that  require  higher 
pressure,  the  sand-blast  pressure  can  be 
readily  throttled  to  the  requirement  of 
its  best  work. 

For  the  different  uses  of  the  vSand 
blast  the  abrasive  substances  may  be  clean 
silicious  sand  as  builders'  sand,  sea-beach 
sand,  emery  from  fine  to  coarse,  chilled  iron  sand,  and  steel 
shot;  sand  from  its  plenteousness  and  general  suitability  is 
mostly  employed.  The  heavier  material,  as  emery  and  chilled 
iron,  require  higher  air  pressure  to  give  the  best  cutting 
velocity. 

The  action  of  the  sand  blast  is  not  cutting,  not  grinding, 
not  abrading  in  any  of  the  usual  meaning  of  these  terms.  It 
is  a  true  pulverization  by  the  successive  impact  of  the  grains  of 
flying  sand.  The  sand  acts  much  in  the  same  manner,  but  on 
an  infinitely  reduced  scale,  as  artillery  projectiles  in  breaching 
a  masonry  wall,  each  independently  of  all  the  rest.  In  this 
action  it  differs  from  anything  that  has  preceded  it,  and  it  still 


Fig.  450.— saxd-blast  tank. 


PNEUMATIC    WORK.  635 

stands  alone.  It  is  this  diiTerence  between  its  action  and  all 
other  processes  that  has  caused  the  general  misunderstanding 
about  it  above  referred  to.  As  all  know,  the  process  consists 
simply  in  driving  a  stream  of  rapidly  moving  sand  against  the 
object  to  be  operated  upon.  How  the  sand  is  given  velocity,  or 
how  the  work  is  presented  to  the  blast,  are  matters  of  indiffer- 
ence when  examining  the  theory  of  the  process.  As  the  total 
action  of  the  blast  is  but  the  summation  of  the  action  of  the 
individual  grains,  the  action  of  the  individual  grain  is  to  be 
considered.  If  the  single  grain  of  the  flying  sand  has  no  effect 
when  it  strikes  the  work,  then  no  other  grains  will  have  any, 
and  the  sand  blast  will  be  without  effect,  no  matter  how  long 
continued.  If,  however,  the  single  grain  of  sand  has  any  effect 
upon  the  object  struck,  then  the  blast  will  wear  it  away,  often 
at  an  extraordinary  speed,  as  the  number  of  grains  propelled 
against  it  is  very  large,  often  as  many  as  5,000,000  per  minute. 

Grains  of  sand  have  numerous  angles,  and  the  action  of 
these  grains— as  also  that  of  the  other  abrasives  mentioned — 
upon  the  surfaces  of  glass,  stone,  or  metal,  is  due  to  the  cir- 
cumstance that  every  individual  grain  in  the  incessant  infinite 
number  in  the  stream  urged  violently  forward  has  all  its  energy 
instantly  arrested,  transferred,  and  concentrated  upon  its  point 
of  impact,  where  it  produces  a  minute  pit  or  depression ;  and, 
as  every  grain  in  the  shower  acts  alike,  the  abrasion  resulting 
from  the  whole  is  perfectly  uniform  in  depth  and  texture  or 
roughness. 

The  action,  moreover,  is  extremely  rapid;  a  momentary  ap- 
plication depolishes  glass  over  any  space  that  can  be  covered  by 
one  stroke  of  the  sand  shower,  instantly  changing  the  previ- 
ously bright  surface  to  obscured  or  that  known  as  ground  glass. 
A  little  longer  exposure  cuts  more  deeply,  and,  with  further 
time,  apertures  are  readily  pierced  through  sheet  and  plate 
glass. 

Stone,  marble,  slate,  and  granite  are  just  as  amenable  to  its 
action.     Iron,  steel,  and  other  metals  have  their  surfaces  easily 


636 


COMPRESSED   AIR   AND    ITS    APPLICATIONS. 


reduced,  and  smoothly  or  coarsely  granulated,  according  to  the 
force  and  abrasive  power  used ;  but  all  these  materials,  being 
less  brittle  than  glass,  take  a  rather  longer  time.  vSpeaking 
generally,  it  appears  that  the  harder  or  more  dense  the  material 
acted  upon,  and  the  higher  the  velocity  given  to  the  sand,  the 

more  rapid  the  cutting  action ; 
and  the  finer  the  abrasion,  and  the 
lower  the  pressure  of  the  air,  the 
finer  the  granulation  produced. 
It  is  also  remarkable,  that  it  is  by 
no  means  necessary  that  the  abra- 
sive be  harder  than  the  material 
to  which  it  is  applied ;  thus,  hard- 
ened steel  and  corundum  are 
readily  pierced  with  sand. 

This  granulating,  scaling,  in- 
cising, and  piercing,  however,  is 
but  one-half  of  the  process,  for,  if 
the  work  be  partly  covered  and 
protected  by  some  slightly  yield- 
ing but  tough  substance,  adhesive  or  in  the  form  of  a  metal 
template  lying  closely  upon  it,  this  interposed  substance  in- 
stantly diffuses  the  shock  of  the  particles  and  neutralizes  their 
abrasive  power.  The  action  of  the  sand  blast  is  thus  confined 
to  the  unprotected  portions  of  the  surface,  and  these  overlays 
and  templates  are  used  on  glass,  stone,  slate,  pottery,  and  metal 
for  surface  ornamentation,  for  deeper  intaglio  and  perforations. 
An  early  exhaust-air  sand-blast  machine  is  illustrated  in 
Fig.  451.  It  had  a  closed  iron  drum  D,  about  20  inches  diam- 
eter, with  an  open  central  pipe  B,  and  below  the  latter  a  verti- 
cally adjustable  plate  P.  The  head  of  the  drum  had  an  aper- 
ture about  4  inches  in  diameter,  closed  by  the  work,  overlay 
downward,  lying  upon  it,  the  exhaust  being  at  E.  The  sand 
from  a  closed  box  falls  down  the  pipe  A  to  the  bottom  of  the 
drum,  on  to  the  plate  P  ;  thence  impelled  or  sucked  up  the  blast 


Fig.  451.— exhaust  sand  blast. 


PNEUMATIC    WORK. 


(>17 


pipe  B  by  the  external  air  rushing  in  above  the  plate  P,  it  strikes 
the  work,  which  is  moved  about  by  the  operator,  who  looks 
through  the  glass  to  watch  the  progress  of  its  frosting.  Most 
of  the  sand  falls  back  to  the  bottom  of  the  drum;  some,  with 
the  dust  pulverized  from  the  glass,  is  carried  along  the  exhaust  to 
a  sand-catch  box.  The  air  pressure  need  not  exceed  one  pound 
to  the  square  inch,  the  frosting  is  almost  instantaneous,  and  the 
hand  may  be  held  in  the  blast  without  inconvenience.  Several 
machines  are  connected  to  one  exhaust  running  round  the 
workshop;  they  are  used  for  small  work,  but  are  applicable  to 
sheets  as  large  as  can  be  conveniently  moved  about  by  two 
men. 

A  small  vacuum  or  exhaust  sand  blast  is  shown  in  Fig.  452. 
It  has  a  bellows  formed  of  a  heavy  plunger  A  connected  to  the 
sides  of  the  drum  by  an  india-rubber  apron  or  diaphragm  and 
by  a  cord  to  a  lever,  by  which  it  is 
operated  like  a  suction  bellows,  the 
valve  E  acting  as  the  discharge 
valve.  The  base  of  the  blast  pipe, 
of  i\  inches  bore,  is  surrounded  by 
a  cup,  5,  pierced  with  holes  below, 
and  beneath  there  is  a  vertically 
adjustable  plate  or  disc.  The  sand 
placed  in  S  falls  on  the  plate,  and 
is  carried  up  by  the  inrush  of  air 
between  that  and  the  lower  end  of 
the  blast  pipe  to  strike  the  work ; 
it  then  falls  and  collects  in  the  base 
of  the  drum.     The  plunger  is  raised 

for  every  impression,  the  lever  being  worked  by  an  assistant, 
sometimes  by  standing  his  weight  upon  it ;  in  smaller  machines, 
it  is  placed  close  to  the  blast,  and  worked  by  the  left  hand,  and 
the  objects  to  be  frosted  are  changed  by  the  right. 

A  form  of  exhaust-air  sand-blast  machine  is  shown  in  Fig. 
453,  in  which  the  drum  has  a  large  exhaust  chamber,  E,  open 


-EXHAUST  SAND  BLAST. 


638 


COMPRESSED   AIR    AND    ITS    APPLICATIONS. 


Fig. 


-VACUUM  SAND  BLAST. 


below  and  worked  from  above;    D  also  carries  the  sand,  whicli 
falls  through  a  pipe,  regulated  by  a  valve,  into  the  open  end  of 

the    tube,    T,    \\    inches    diameter, 
c  which,     bent     upward,     terminatec 

within  the  open  bell  mouth  of  the 
lower  end  of  the  blast  pipe  B,  2 
inches  diameter,  outside  the  drum. 
The  upper  end  of  B  is  contained 
within  a  box,  called  the  working 
chamber,  provided  with  an  aperture 
above,  upon  which  the  glass  is 
placed.  The  sand  carried  up  T,  by 
the  current  induced  by  the  exhaust, 
as  it  issues  is  caught  by  the  stronger 
current  of  external  air  entering  all 
around  the  open  bell  mouth  of  B, 
and  thus  accelerated  travels  upward  and  strikes  the  work.  The 
exhaust  then  carries  the  spent  air  and  sand  from  the  working 
chamber,  W,  to  the  annular  space 
D\  here  both  circulate  spirall}' 
around,  and  to  the  bottom  of  E, 
the  heavier  particles  of  sand  strik- 
ing the  sides  of  D  by  centrifugal 
force,  and  falling  to  the  bottom,  the 
lighter  particles  and  the  dust  pulver- 
ized from  the  glass,  travelling  with 
the  air  up  within  E,  and  along  the 
exhaust  pipe  E.  Virtually  free 
from  the  escape  of  sand,  the  ma- 
chine almost  entirely  sifts  the  dust 
from  the  sand,  which  latter  is  used 
again  and  again.  Large  sheets  of 
glazing  glass,  covered  with  their  overlay  designs,  are  thus 
frosted  to  the  form  of  the  pattern. 

In  Fig.  454  are  represented  two  forms  of  pressure  air  sand- 


FlG.    454.— PRESSURE  SAND   BLAST. 


PNEUMATIC    WORK. 


639 


blast  nozzles.  These  nozzles  have  been  made  as  round  and 
flat  blast  pipes,  which  postpone  the  mingling  of  the  air  with  the 
sand  until  both  have  issued  from  the  nozzle.  The  straight  pipe 
in  the  upper  portion  of  Fig.  454  represents  the  pipe  through 
which  the  sand  arrives  by  gravity  or  otherwise;  this  is  sur- 
rounded by  the  enlarged  hollow  head  of  the  air  pipe,  A,  the 
one  adjustable  lengthwise  within  the  other  to  determine  the 
extent  of  the  annular  space  between  their  open  tapering  ends; 
the  air  rushing  up  A  issues  through  this  space,  and,  converging, 
catches  up  and  carries  the  sand  for- 
ward, the  two  only  mingling  at  the 
point  shown  by  the  vertical  dotted 
line,  well  beyond  the  end  of  the 
nozzle. 

The  lower  figure  represents  this 
principle  with  a  sand  box  and  valve 
attached  which  can  be  operated  by 
the  thumb  as  the  hand  grasps  the 
handle. 

A  form  of  sand-blast  cylinder 
which  allows  of  recharging  without 
interrupting  the  operation  of  the 
sand    blast    is    illustrated    in    Fig. 

45  5- 

The     external     cylinder,    D,    is     fig.    455.-AIR-LOCK   sand-blast 

TANK. 

divided   into    three    compartments, 

two  air-tight  and  the  topmost  a  hopper  open  above.  The 
sand,  shovelled  through  a  sieve  in  this  last,  falls  through 
valves  into  compartment  2,  thence  through  similar  valves  into 
the  open-mouthed  sand  box,  S,  fixed  in  compartment  3,  and 
from  this  through  a  funnel-mouthed  pipe  into  the  open  end  of 
the  delivery  pipe,  B.  The  compressed  air  enters  at  A,  fills 
compartment  3,  inclusive  of  the  space  above  the  sand  in  the 
box  5,  and  dries  the  sand  as  it  falls  from  the  latter  along  B  to 
the  blast  pipe,  a  piece  of  plain  chilled  iron  or  steel  tube  from 


640  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

T6  ^°  i-inch  bore,  which  is  held  in  the  hand  at  the  further  end 
of  a  length  of  flexible  hose  attached  to  the  end  of  B.  The  sand 
in  5  being  in  equilibrium  as  regards  pressure  of  air,  falls  freely 
by  gravity ;  its  volume  is  regulated  by  a  screw  sliding  valve,  the 
head  of  which  is  outside  the  drum.  Compartment  2  is  also 
filled  with  compressed  air  from  a  branch  of  the  pipe  A,  but  this 
is  allowed  to  escape  by  the  relief  valve  in  order  to  open  the 
valve  in  the  hopper  every  time  fresh  sand  is  added,  so  that  the 
issue  of  the  sand  blast  is  continuous  and  uninterrupted.  The 
recent  improvements  and  inventions  of  Air.  Matthewson,  man- 
ager of  the  Tilghman  Sand  Blast  Company,  Sheffield,  England, 
have  given  a  new  impetus  to  the  use  of  the  sand  blast  for  a 
great  variety  of  purposes.  In  these  machines  the  best  points 
have  been  retained,  and  there  has  been  secured  also  the  full 
efficiency  of  the  blast,  due  to  the  pressure  at  which  it  is  used, 
unreduced  by  the  admixture  of  any  dead  air  carrying  the  sand 
with  it,  at  just  the  place  where  the  maximum  velocity  is  de- 
sired. This  machine  uses  air  at  all  pressures,  but  those  about 
ten  pounds  to  the  square  inch  are  found  to  be  the  most  satisfac- 
tory. By  immersing  the  whole  sand  supply  in  an  atmosphere 
of  air  at  the  above  pressure,  contained  in  a  tight  reservoir,  the 
advantages  of  a  pure  gravity  feed  are  obtained,  uncomplicated 
by  any  questions  of  difference  in  pressure  inside  of  the  jet  tubes 
and  without.  Then,  by  the  use  of  a  flexible  tube  of  considera- 
ble diameter,  the  sand  and  air,  in  a  mixed  current,  are  carried 
to  a  point  where  they  are  to  be  used.  Here  the  flexible  tube  is 
connected  with  a  hard  chilled  iron  cone,  terminating  in  a  tube 
of  small  diameter.  In  traversing  this  latter  portion  of  its 
course  the  mixed  current  of  sand  and  air  increases  its  velocity 
inversely  as  the  square  of  the  diameter  of  the  tube,  and  is 
finally  discharged  from  the  end  of  the  blast  nozzle  at  the  full 
velocity  due  to  the  pressure  behind  it.  An  air-lock  arrange- 
ment for  transferring  new  supplies  of  sand  into  the  sand  re- 
servoir, while  still  under  pressure,  and  valves  for  operating 
and  graduating  the  air  and  sand  supply,  with  a  suitable  com- 


PNEUMATIC   WORK.  64I 

pressor  for  furnishing  the  supply  of  compressed  air,  complete 
the  arrangement. 

In  metal  it  is  used  for  the  removal  of  the  hard  scale,  so  de- 
structive to  cutting  tools,  from  castings  and  forgings.  Among 
the  applications  are  the  removal  of  the  scale  from  sheet  iron 
and  steel  prior  to  enamelling,  galvanizing,  nickelling,  tinning, 
etc. ;  the  cleaning  of  tubes  and  brazed  joints,  largely  used  in 
bicycle  work ;  sharpening  the  teeth  of  files ;  for  granulating  or 
frosting  electroplate,  gilding  metal,  gold-  and  silversmiths'  work, 
and  jewelry ;  the  reduction  to  clean  metal  surfaces  of  larger 
works,  ranging  from  steel  forgings  of  safes  to  armor  plates;  on 
stone,  slate,  and  granite,  for  incised  carvings  and  inscriptions 
in  intaglio  or  relief;  for  cleaning  off  the  grime  from  stone, 
granite,  and  brick  buildings,  and,  in  contrast  to  this  last,  for  the 
most  delicate  drawing  for  lithography. 

Among  other  purposes  it  is  employed  for  removing  fur  and 
deposits  in  tubes  and  tanks ;  for  cleaning  off  accumulations  of 
paint  and  dirt  within  iron  ships;  for  roughening  the  surfaces 
of  metal  rollers;  for  decorating  coat  and  other  buttons;  for 
granulating  glass  to  give  it  a  key  for  ornamental  painting  by 
hand ;  for  piercing  the  apertures  in  glass  ventilators  ;  for  mark- 
ing cakes  of  glue  and  cement;  for  marking  pottery  and  in  the 
manufacture  of  ornamental  tiles;  for  smooth-facing  bricks  to 
receive  white  glass  or  enamel ;  for  refacing  grindstones,  emery, 
and  corundum  wheels ;  for  granulating  celluloid  films  for  pho- 
tography, and  on  wood  to  bring  out  the  grain  in  relief,  and 
latterly  for  blocks  for  printing. 

For  stone,  marble,  slate,  and  granite,  the  abrasives  are  sand, 
emery,  and  chilled  iron  sand,  delivered  at  from  10  to  15  pounds 
pressure,  usually  from  the  compressed-air  apparatus  already 
described.  The  overlays  are  similar  to  those  for  glass;  if  for 
original  designs,  they  are  cut  of  thick  porous  paper  saturated  with 
the  glue  and  dextrine,  by  which  also  they  attach  to  the  plain  or 
polished  stone;  for  work  often  repeated  they  are  frequently 
iron  stencil  plates.  The  quick,  yet  gentle  action  of  the  process 
41 


642  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

annuls  all  risk  of  "plucking"  or  splaying  the  stone;  but  in 
some  materials  and  marbles  and  in  granite,  which  may  be  con- 
sidered conglomerates,  the  harder  are  rather  less  cut  away  than 
the  softer  constituents;  the  sparkling  granulation  then  pro- 
duced is  itself  decorative,  but,  if  required,  it  may  subsequently 
be  smoothed  and  polished. 

Granulating  designs  with  overlays  and  frosting  on  moderate- 
sized  works  in  metal  are  generally  conducted  within  a  closed 
drum  or  box  glazed  on  one  or  more  sides  to  watch  progress,  and 
with  holes  in  the  sides  of  the  box  with  elastic  sleeves  for  the 
hands  to  hold  the  work  in  the  vertical  sand  blast. 

A  beautiful  translucent  variety,  known  as  chip  or  crystalline 
glazing  glass,  covered  with  gray  filaments  and  fern  and  feath- 
ery markings  on  an  ice-like  ground — is  also  remarkable  for  the 
peculiarities  of  its  manufacture.  The  surface,  first  uniformly 
frosted  with  the  sand  blast,  is  then  covered  with  a  coat  of 
strong  glue,  and  when  this  has  set,  the  sheets  are  placed  in 
horizontal  racks  in  a  room  heated  to  160°.  In  the  course  of  ten 
or  twelve  hours,  the  hardening  glue  audibly  cracks  and  springs 
off  in  patches,  bringing  away  thin  flakes  of  the  glass  with  it. 
The  fern-like  markings  are  irregular  portions  of  the  original 
sand-blasted  surface  which  remain  on  these  flat  conchoidal 
fractures. 

This  simple  process  was  discovered  by  an  accident,  and 
put  to  use  by  Mr.  Corsan  in  England.  Beyond  the  curious  fact 
that  glue,  under  such  conditions,  will  tear  flakes  from  glass, 
the  explanation  appears  to  be  that  the  hardening  glue  gradu- 
ally blisters,  and  these  blisters,  as  they  detach,  tear  off  more  of 
the  glass  by  their  margins  than  toward  their  central  portions, 
which  latter  leave  the  fern-like  markings.  By  the  employment 
of  the  ordinary  overlays  prior  to  frosting  and  gluing,  the  crys- 
talline effect  is  sharply  localized  and  confined  to  any  portion  of 
a  design. 

Lamp  globes  and  spherical  objects  are  plain  or  pattern- 
frosted  all  over  their  superficies  in  an  ingenious  manner.     The 


PNEUMATIC    WORK, 


643 


drum  of  the  machine — about  as  high  as  its  diameter — has  a 
hinged  cover,  and  moves  round  on  a  central  vertical  pivot. 
Diametrically  within  the  drum  is  a  spindle,  or  rather  the  two 
ends  of  a  spindle,  its  central  portion  removed  and  replaced  bj' 
corresponding  rods,  with  spring  means  of  holding,  which  carry 
the  glass  globes.  The  globe  when  in  its  place  is  exactly  in  the 
centre  of  the  drum,  and  the  tube  of  the  sand  blast,  presented 
horizontally,  points  to  the  centre 
of  the  globe.  During  the  frOvSting 
the  spindle  is  continuously  turned, 
and  the  drum  itself  moved  round 
on  its  pivot  through  about  a  half- 
circle,  both  automatically ;  the  cen- 
tral line  of  the  spreading  sand 
shower — its  most  active  part — thus 
always  points  to  the  axis  of  the 
globe,  which  secures  absolute  uni- 
formity in  the  texture  of  the  frost- 
ing. Dry  sand  and  air,  at  about  one 
pound  pressure,  are  used  for  ordi- 
nary work,  and  very  fine  sand,  with 
steam  at  about  20  pounds  pressure, 

for  the  best  class  of  this  work.     The  globes  are  replaced  with 
expedition,  and  from  60  to  100  may  be  completed  in  an  hour. 

In  ordinary  lithography  the  design  is  drawn  on  the  pure, 
smooth,  polished  stone  in  a  greasy  chalk  or  ink,  and,  although 
almost  inappreciably,  really  stands  just  in  relief;  when  printed 
from,  the  stone  is  kept  constantly  wet  with  water,  which  repels 
the  ink — applied  with  a  roller — from  all  parts  of  its  surface,  ex- 
cept the  greasy  lines  of  the  drawing ;  upon  these  the  water  can- 
not stay,  and  they  alone  receive  the  ink  and  print. 

In  sand-blast  lithography  this  is  partly  reversed.  The 
whole  surface  of  the  stone  is  first  impregnated  with  grease,  so 
that,  if  then  inked,  it  would  print  a  uniform  black;  and  this 
surface  is  then  eaten  away  to  a  trifling. depth  with  the  sand 


Fig.  456.— drum  sand  blast. 


644  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

blast,  to  entirely  remove  the  grease  from  all  portions  that  are 
not  to  print,  that  is,  which  are  to  give  white ;  to  granulate,  or 
more  or  less  destroy  it  upon  those  to  give  different  tones  of 
shading;  and  to  leave  it  intact  upon  those  that  are  to  print 
black.  All  that  remains  of  the  original  greased  surface,  there- 
fore, alone  prints;  the  stones  being  wetted,  as  usual,  prior  to 
inking  for  every  impression. 

Sand-blast  engraving  has  been  tried  for  steel-plate  printing, 
and,  although  still  in  the  experimental  stage,  it  gives  good 
promise  of  a  future.  The  granulation  from  the  fine  emery 
powder  gives  the  character  of  a  mezzotint,  but  unlike  an  ordi- 
nary plate,  upon  which  the  rocking  is  generally  uniform,   so 

^. — ~ ~ ~l      that   it   would   print    a    solid 

^e;.        '^-^i: — ~     ^  block,    and   is    then    reduced 

in  tones  by  scraping  and  bur- 
nishing to  produce  the  draw- 
ing, the  granulation  of  the 
sand   blast   may  be  localized 

Fig.  457.— the  file  sand  blast. 

and  arrested  on  any  portion 
at  any  depth  of  tint;  thus  reducing  the  subsequent  scraping  to 
a  minimum.  In  printing,  the  plates  are  treated  just  in  the  or- 
dinary manner;  the  whole  surface  is  inked,  wiped  clean  of  the 
ink,  and  finally  polished  with  whiting  on  the  palm  of  the  hand. 
Worn-down  files  are  resharpened  in  the  sand  blast  by  being 
slowly,  drawn  several  times  from  tang  to  point  between  two 
converging  streams  of  fine  sand — sand  worn  so  fine  in  grinding 
plate  glass  as  to  have  become  valueless  for  that  purpose,  and  a 
waste  product,  is  preferred — projected  by  compressed  air  at  about 
60  pounds  pressure,  which  pass  on  from  the  file  into  a  receptacle 
for  reuse.  The  effect  is  rapid,  and  on  both  sides  of  a  flat  or  on 
all  four  sides  of  a  square  file  simultaneously,  a  fourteen-inch 
rough  or  bastard  file  being  resharpened  in  two  or  three  minutes ; 
on  second  cut  and  smooth  files  the  blast  acts  still  more  quickly, 
blasting  away  the  curves  until  they  again  meet  the  upright 
sides  of  the  teeth,    and  at  but  little  less  angle  than  before. 


PNEUMATIC    WORK. 


645 


The  file  throughout  the  process  is  drawn  across  a  piece  of  gun 
metal  fixed  between  the  sand  blasts,  and  the  equal  hang  of  the 
teeth  to  this  "  feeling  piece  "  tells  the  operator  the  resharpen- 
ing  is  uniform  from  end  to  end. 

The  thorough  work  of  the  sand  blast  has  been  recently  dem- 
onstrated in  the  cleaning  of  old  paint  and  dirt  from  structural 
steel  work  for  preparing  it  for  repainting,  the  structure  being 
the  viaduct  at  One  Hundred  and  Fifty-fifth  Street,  New  York 


Fig.  458.— sharpening  files. 


City,  which  had  been  painted  many  times  to  prevent  injury  to 
the  steel  trestle-work  by  the  smoke  and  gases  of  the  Elevated 
Railway  locomotives.  Rusting  had  taken  place  under  the  many 
coatings  of  paint,  and  blistering  and  peeling  had  given  the 
work  an  unsightly  appearance  with  indication  of  damage  to  the 
structure.  For  this  work  compressed  air  was  conveyed  about 
300  feet  from  a  compressor  to  a  receiver,  and  to  the  sand-mixing 
apparatus  on  a  temporary  flooring  in  the  trusses  of  the  viaduct. 


646  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

A  hose  connects  the  sand-mixer  and  nozzle,  which  was  held 
close  to  the  surface  to  be  cleaned.  A  section  of  the  trusses  was 
made  perfectly  clean  in  the  early  part  of  the  day,  and  at  once 
painted  by  the  air-blast  process,  thus  giving  the  paint  a  perfect 
contact  with  the  metal  and  by  this  means  obviating  the  formation 
of  rust  from  loose  scale. 

For  cleaning  the  walls  and  trimmings  of  buildings  the  sand 
blast  has  proved  a  perfect  success.  For  removing  the  smoke 
and  fire  stains  on  the  walls  of  buildings  that  have  been  burned 
and  are  found  safe  for  rebuilding,  the  sand  blast  has  been  a 
saving  clause  in  the  expense  of  rebuilding,  as  was  tested  in 
cleaning  the  walls  of  Pardee  Hall,  Lafayette  College,  at  Easton, 
Pa.  The  stone  facing  and  trimmings  of  the  New  York  Central 
&  Hudson  River  Railway  station  in  New  York  City  have  under- 
gone a  most  satisfactory  renewal  by  the  sand-blast  process. 

The  air  blast  finds  one  of  its  useful  effects  in  sanding  paint 
on  car  roofs  and  buildings  wherever  sanded  paint  is  needed  for 
special  protection.  The  sand  thus  thrown  with  great  force  im- 
beds itself  in  the  paint,  and  the  air  blast  without  the  sand 
blows  off  the  excess. 

The  air  blast  is  also  used  for  feeding  coal  dust  and  fine 
culm  to  boiler  and  other  furnaces,  and  in  the  petroleum  burner 
with  its  steam  combination  it  contributes  a  most  important 
condition  in  the  combustion  of  liquid  fuel. 

Fig.  459  illustrates  a  petroleum  burner,  for  a  furnace,  for  a 
boiler,  or  other  requirements.  A,  entrance  of  oil  to  central 
nozzle,  which  is  regulated  by  a  needle  valve  with  screw  spindle 
and  wheel,  C  ;  B,  entrance  of  compressed  air  to  the  annular 
nozzle,  the  force  of  which  draws  the  oil  and  atomizes  it  for 
quick  combustion. 

The  air  blast  is  also  used  for  elevating,  drying,  and  aerating 
grain,  for  elevating  coal  culm,  and  discharging  ashes. 

Compressed  air  is  also  used  for  discharging  the  oil  from 
tank  cars  to  a  higher  level  by  sealing  the  manhole  and  forcing 
air  above  the  oil. 


PNEUMATIC    WORK,  647 

The  discharge  of  sand,  soft  material,  and  water  from  the 
foundation  caissons  of  bridge  piers  by  the  direct  action  of  com- 
pressed air  has  become  a  most  important  adjunct  in  caisson 
sinking,  and  was  used  in  sinking  the  caissons  of  the  Brooklyn 
and  New  York  bridges  to  great  advantage.  A  pipe,  usually 
about  four  inches,  is  inserted  in  the 
roof  of  the  caisson,  extending  up 
through  the  loading  masonry  and 
overboard  to  a  scow.  The  lower 
end  is  extended  down  to  a  sump, 
with  a  quick-opening  gate.  The 
sump  is  used  for  a  drain  basin,  into 

Fig.  459.— petroleum  burner. 

which    sand,    clay,    and    mud    are 

thrown  and  ejected  with  great  velocity  by  the  air  pressure  in 
the  caisson;  the  air  lock  being  used  for  the  passage  of  the 
men,  tools,  and  material  required  for  the  sub-masonry. 

THE   AIR    BLAST   IN    PAINTING. 

The  air  blast  for  painting  is  comparatively  a  late  innovation 
in  the  old  and  staid  art  of  wielding  the  paint-brush  by  hand; 
but  the  times  are  progressive,  and  the  use  of  compressed  air  in 
the  arts  keeps  pace  with  its  extending  use  in  mechanics.  Like 
all  other  progressive  movements  leading  to  new  ways  and 
means,  this  is  also  a  labor-saving  operation  and  is  becoming  an 
important  and  economical  helper  in  the  work  of  painting.  For 
structural  work,  bridges,  and  the  painting  of  railway  cars,  it 
is  gaining  a  fast  foothold  for  good  and  economical  service.  Tt 
is  not  only  used  for  oil  painting,  but  has  proved  a  most  efficient 
method  of  whitewashing  and  kalsomining  walls  and  fences. 
Further,  the  finer  points  of  the  artist's  conceptions  have  taken 
the  air  blast  in  hand  for  pictorial  illustration.  The  atomizing 
of  colored  fluids  in  a  spray  from  sharp  lines  to  faint  shadows  is 
the  outcome  of  the  air-blast  process,  which  has  been  applied  to 
the  production  of  picture  work. 


648 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  460.— hand    air   painT' 

POT. 


The  simple  hand  compressed-air  paint-pot  is  shown  in  Fig. 
460.  The  thumb  key  is  for  regulating  the  air  blast,  and  the 
valve  wheel  at  the  left  side  regulates  the  flow  of  the  paint. 
The  paint  pipe  starts  from  the  bottom  of  the  can  and  joins  the 

air   pipe   and   spray   nozzle   as   shown   in 
the  cut. 

Fig.  461  represents  a  paint-spray 
nozzle  as  usually  constructed.  The  inner 
or  air  nozzle,  usually  i-inch  opening,  is 
made  on  the  best  lines  for  high  air  veloc- 
ity and  is  fixed  central  to  the  larger  open- 
ing in  the  inverted  conical  nosepiece, 
which  is  flattened  to  a  thin  opening,  g^  inch,  to  project  the  paint 
spray  in  a  thin  .sheet.  The  paint  is  drawn  in  at  the  side  inlet 
of  the  tee  piece,  and  both  air  pressure  and  paint  supply  are 
regulated  by  valves,  both  pipes  being  under  the  same  pressure 
from  the  paint  tank  of  from  50  to  80  pounds  per  square  inch. 

In  Fig.  462  is  detailed  the  Mason  painting  machine,  which 
consists  of  a  steel  paint  tank  strong  enough  for  a  working  press- 
ure of  100  pounds  per  square  inch;  a  small  hand  air  pump 
mounted  upon  the  top  of  the  tank,  with  suction  and  pressure 
pipes  connected  to  the  top 
of  the  tank  in  which  are  the 
three-way  cocks  A  and  B. 
To  the  tank  connection  at  F 
is  a  pressure  gauge  and  the 
air  pipe  and  cock  at   C.     E 

is  the  paint  discharge  pipe.      The  tank  is  charged  from  the  mix- 
ing barrel  by  the  siphon  and  cock  D. 

The  operation,  then,  is  as  follows:  to  charge  the  tank,  the 
cock  D  is  closed,  the  three-way  cock  A  is  turned  to  communi- 
cate the  suction  of  the  pump  with  the  tank.  The  three-way 
cock  B  is  turned  to  discharge  the  air  at  its  side  outlet  with  clos- 
ure on  the  tank,  the  cock  C  being  closed.  The  pump  is  then 
operated  to  exhaust  the  air  from  the  tank,  producing  a  degree 


Fig   461.— paixt  spray  nozzle. 


PNEUMATIC    WORK. 


649 


of  vacuum  measured  by  the  gauge,  which  is  both  a  vacuum  and 
pressure  gauge.  The  cock  D  is  then  opened,  and  the  paint 
mixture  is  drawn  into  the  tank  in  the  desired  quantity,  or  for 
continuous  work  about  two-thirds  full.  Cock  D  is  then  closed: 
cock  A  is  turned  to  shut  off  the  tank  connection  and  to  draw  air 
from  the  side  inlet ;  cock  B  turned  to  connect  with  tank  and 
shut  off  side  exit.  The  pump  can  then  be  operated  to  charge 
the  tank  with  the  desired  air  press- 
ure. For  operating  the  spray,  the 
paint  hose  is  connected  to  the  cock 
E  at  the  bottom  of  the  tank  and  the 
air  pipe  to  the  cock  C  at  the  top  of 
the  tank  with  the  valves  on  the 
spray  nozzle  closed.  The  cocks  C 
and  E  are  then  opened,  which  gives 
a  balanced  pressure  in  both  pipes. 
When  ready,  open  the  air  valve  on 
the  spray  nozzle,  and  then  the  paint 
valve  to  meet  the  requirement  of 
the  spray.  The  ejector  power  in 
the  nozzle  draws  the  paint  by  over- 
coming the  static  pressure. 

By  varying  the  opening  of  the 
valves  of  the  spray  nozzle  any  den- 
sity of  the  spray  may  be  had  from 
a  thin  cloud  to  a  solid  paint  stream. 
The  air  pump  must  be  kept  in  operation  to  keep  up  the  press- 
ure according  to  the  relative  proportion  of  air  and  paint  ejected. 
The  nozzle  should  be  moved  slowly  broadside  over  the  work; 
a  jerky  motion  scatters  the  paint.  The  same  machine  works 
equally  well  with  whitewash  or  kalsomine. 

In  Fig.  463  we  illustrate  the  Mason  painting  machine  as 
operated  by  an  electric  motor  belted  and  geared  to  a  triplex 
air  pump.  By  this  arrangement  the  motor  and  pump  can  be 
placed  in  a  convenient  location  for  electrical  connection    and 


c5lDE   E'LlVATIOfJ^ 

Fig.  462.— mason  i>ainting  machine. 


6;o 


COMrRESSED    AIR   AND    ITS   APPLICATIONS. 


PNEUMATIC   WORK. 


651 


the  hose  extended  to  the  tank,  which  should  be  in  proximity  to 
the  work. 

In  Fig.  464  we   illustrate  the  magnite  spray  painting  ma- 
chine made  by  J.  A.  and  W.  Bird  &  Co.,  Boston,  Mass.     It  is 


Fig.  465.— pneumatic  paint  machine. 

Used  as  a  hand  painting-machine  for  car  and  structural  iron  painting.  A  record  of  four- 
teen minutes  has  been  made  with  one  of  these  machines  in  painting  an  ordinary  box  car. 
They  are  made  by  the  Chicago  Pneumatic  Tool  Company. 


a  portable  machine,  having  all  its  parts  mounted  on  a  platform 
with  casters.  A  two-cylinder  air  pump  with  single-acting  trunk 
pistons  operated  by  a  hand  lever,  and  with  an  air  receiver 
and  pressure  gauge,  constitute  it  a  very  simple  and  complete 
apparatus  for  spray  painting  with  oil  paints,   kalsomine,   and 

r 


Fig.  466.— car-deck  painting. 


652 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Fig.  467.— car-side  painting. 


Other  water  paints,  and  for  spraying  antiseptics  in  hospitals, 
cellars,  and  on  brewery  walls.  In  fact,  there  seems  to  be  no 
end    to    the    uses    that  an  atomizing    machine  can  be  utilized 

for.  Paint  machines  are 
readily  cleaned  by  pump- 
ing naphtha  through 
them,  discharging  back 
into  the  tank. 

The  spray  painting  of 
railway  cars  has  now  be- 
c  o  m  e  an  accomplished 
fact,  and  is  in  practice  on 
a  number  of  railways. 
We  call  attention  to 
the  fact  that  a  perfectly  atomized  sprayed-on  paint  will  almost 
instantaneously  reach,  cover  up,  and  consequently  protect  a 
car's  most  complicated  structural  parts.  It  penetrates  the  rough 
beaded  work — the  open  joints  through  shrinkage  of  sheathing 
— the  crevices  and  other  disfigurements  usually  met  with  when 
painting  the  new  and  repainting 
the  old  railway  freight-car  equip- 
ment. 

There  is  evidence  of  the  close 
observation  made,  from  time  to 
time,  of  sprayed  freight  cars  and 
other  large  surface  work  done  by 
the  P.  &  L.  E.  R.  R.  Company,  in 
the  beginning,  convincing  us  that 
the  results  from  a  standpoint  of 
durability  will  not  suffer  on  the  score  of  fact  that  the  paint 
was  not  applied  with  a  brush. 


Fig.  46S.— truck  p.\ixtixg. 


PNEUMATIC    WORK. 


653 


Fig.  469.— cukv^ed  nozzle. 


COMPRESSED    AIR    FOR    DUSTING   AND    CLEANING. 

A  novelty  among  the  several  hundred  applications  of  com- 
pressed air  for  useful  work  and  for  time-saving  in  labor,  is  the 
air  blast.  It  is  only  in  recent  years  that  the  power  of  the  air 
blast  has  been  used  for  cleaning  the  dust 
from  carpets,  walls,  ceilings,  furniture, 
car  seats,  and,  in  fact,  every  place  where 
dust  can  find  a  hiding-place.  Not  only 
this,  but  where  disinfectants  are  needed 
the  air  blast  is  the  most  convenient  vehi- 
cle for  their  distribution  for  best  effect. 
In  this  manner  dwellings  and  public  build- 
ings may  be  quickly  and  cheaply  renovated  even  to  the  dra- 
peries and  bedding.  Air  can  now  be  bottled  at  3,000  pounds 
pressure  per  square  inch,  and  thus  made  portable  to  be  con- 
veyed for  use  in  any  locality.  Where  an  electric  current  can 
be  utilized,  an  electric  motor  becomes  a  part  of  the  house-clean- 
ing kit  for  compressing  the  air.  A  gasoline-motor  compressor 
on  a  light  wagon  becomes  a  complete  portable  outfit  for  house- 
cleaning,  only  requiring  the  ex- 
tension of  its  air  hose  to  the 
rooms  or  localities  to  be  cleaned. 
In  Fig.  469  is  illustrated  the 
form  of  an  air-spray  nozzle  for 
dusting  with  compressed  air. 
This  is  a  broad,  thin  nozzle  from 
which  a  blast  of  compressed 
air  penetrates  fabrics,  cleaning 
them  of  dust;  a  good  cleaner 
of  plain  and  carved  woodwork.  The  open  slit  should  vary  in 
width  from  one-thirty-second  to  one-sixteenth  of  an  inch,  and 
in  breadth  from  one  to  six  or  more  inches,  according  to  the  kind 
of  work  it  is  to  do. 

The  straight-edge  nozzle  (Fig.  470)  is  the  most  suitable  for 


Fig.  470.— str.\ight  nozzle. 


654 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


flat  work  such  as  car-seat  cushions  and  carpets  that  are  dusted 
out-of-doors. 

In  Fig.  471  is  illustrated  a  suction  nozzle  in  which  the  com- 
pressed air  is  ejected  against  the  point  of  the  inverted  cone, 


Fig.  471.— suction  nozzle. 


which  induces  a  strong  current  of  air  upward  and  from  under 
the  bottom  of  the  inverted  funnel,  drawing  the  dust  from  the 
fabric  and  projecting  it  through  a  hose  out  of  the  windows; 
much  used  in  car-seat  cleaning. 

For  carpet-cleaning  in  dwellings  where  it  is  not  convenient 
to  use  a  hose  for  ejecting  the  dust  through  the  windows,  a  filter 
hood  or  dust  collector  is  used,  which  allows  the  air  to  pass 
through,  retaining  the  dust  on  the  inside.  The  filter  hood  is  to 
be  taken  outside  and  cleaned  when 
it  becomes  charged  with  dust. 

The  carpet-cleaner  as  illustrated 
is  a  box-shaped  arrangement  into 
which  is  injected  a  blast  of  air  twelve 
inches  long  and  one-hundredth  of  an 
inch  wide.  This  blast  strikes  the 
carpet  at  an  angle  of  45°  under  a 
pressure  of  75  pounds  per  square  inch, 
removing  all  the  dust  from  the  carpet 
and  depositing  it  in  the  receptacle.  The  cleaner  is  pushed  over 
the  carpet  the  same  as  an  ordinary  sweeper,  and,  besides  re- 
moving all  dust,  the  effect  of  the  compressed  air  is  to  restore 
the  carpet  to  its  original  color. 

The  cleaning  of  dwelling-houses  and  hospitals  and  the  dis- 


»~-teSC*5»^TSJ»r'' 


Fig.  472.— filter  hood. 


PNEUMATIC    WORK.  655 

infection  of  walls,  carpets,  and  furniture  are  coming  largely  into 
practice  with  the  best  results,  and  are  now  being  conducted  by 
the  General  Compressed-Air  House-Cleaning  Company,  St. 
Louis,  Islo. 

In  Figs.  472  and  474  is  shown  the  disinfecting  attachment 
on  the  pipe  handle  of  the  air-blast  machine.  A  glass  reservoir, 
somewhat  like  an  automatic  oil    cup,   is  attached  to  the  pipe 


Fig.  473.— carpet  cleaning  with  the  filter  hood. 

handle,  with  an  air  connection  both  above  and  below  the  fluid 
with  a  cock  to  regulate  the  flow  of  the  disinfectant. 

For  spraying  walls  and  ceilings  the  reservoir  connection  is 
inverted  and  a  spray  nozzle  takes  the  place  of  the  box. 

In  Figs.  475  and  476  is  illustrated  a  machine  for  cleaning 
and  removing  dust  from  carpets  and  other  similar  fabrics  by 
the  air-blast  process ;  it  is  in  use  in  carpet-cleaning  establish- 
ments. 

Hitherto,  when  machinery  has  been  used  for  this  purpose, 
the  system   employed  has  merely  been   an  amplification  of  the 


656 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


crude  method  of  hand-beating,  sticks,  chains,  straps,  or  ropes 
being  used.  Carpets  submitted  to  this  beating  or  "hammering" 
process  are  frequently  torn  and  otherwise  damaged ;  holes  are 
enlarged,  and  worn,  tender  places  are  made  into  holes.  In  the 
air  process  illustrated  all  chance  of  damage  is  eliminated,  as 

no  form  of  beating 
whatever  is  resorted  to, 
the  cleansing  being  ef- 
fected solely  by  the 
use  of  minute  jets  of 
compressed  air  driven 
at  a  pressure  of  45 
to  50  pounds  per  square 
inch  entirely  through 
the  fabric.  These 
carry  along  with  them 
every  particle  of  dust 
from  the  carpet  with- 
out any  damage  what- 
ever. The  illustration 
(Fig.  475)  represents  an 
elevation  of  the  pneu- 
matic carpet-cleaning 
machine,  and  Fig.  476 
an  elevation  at  the  driv- 
ing end  of  the  machine. 
From  these  it  will  be 
seen  that  nearly  the  whole  of  the  machine  is  enclosed  in  a 
hexagonal  casing  provided  at  each  side  with  swing  doors  for 
the  insertion  and  withdrawal  of  the  carpets.  Compressed  air 
is  conveyed  from  the  main  pipe  by  means  of  the  two  flexible 
branch  pipes  to  the  longitudinal  feeder  pipe  running  the  entire 
length  of  the  machine.  This  pipe  is  fitted  at  intervals  of  two 
inches  with  a  number  of  nozzles,  each  having  small  holes  at  its 
nose,  through  which  the  compressed  air  escapes  in  minute  jets 


Fig.  474.— DisixFEcri.xG  attachmk.nts. 


PNEUMATIC    WORK. 


657 

at  great  velocity,  onto  and  through  the  carpet.     This  is  carried 
slowly  under  the  jets  by  the  central  wire  roller,  to  which  a 


Fig.  475.— carpet-cleaning  machine. 

rotary  motion  is  given  by  the  bevel  wheels  and  driving  pulleys 
shown.  After  the  carpet  has  once  been  passed  through  the 
machine  by  the  roller,  if  found  desirable — as  in  the  case  of  very 
thick  carpets — it  can  be  passed  through  a  second  time  by  revers- 
ing the  action  of  the  revolving  roller.  The  feeder  pipe  carry- 
ing the  nozzles  rides  at  each  end  on  trunnions,  carried  b}-  an 
upright  lever  and  shaft,  to  which  an  oscillating  motion  sidewise 
is  given  from  the  driving  shaft  by  an  eccentric  and  rod ;    the 


I    \m. 


object  of  this  oscillation  is  to 
thoroughly  distribute  the  air 
currents  over  the  entire  surface 
of  the  carpets  passing  under  it. 
This  pipe  is  further  divided  into 
two  unequal  sections,  from  either 
of  which  the  compressed  air  can 
be  shut  off  when  carpets  narrower 
than  the  full  width  of  the  ma- 
chine are  being  cleaned.  The 
whole  of  the  dust  removed  from 
the  carpets,  by  the  action  of  the 
compressed  air  thereon,  is  drawn  away  from  the  machine  by  an 
air  propeller  or  exhaust  fan  at  the  left-hand  side ;  the  dust  being 

delivered  into  a  chimney,  flue,  or  other  suitable  receptacle. 

42 


Fig.  476  —end  view. 


658 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


5  ^ 


..■^      i, 


PNEUMATIC    WORK.  659 

By  this  method,  carpets  are  cleaned  so  effectually  that  any 
amount  of  beating  afterward  fails  to  extract  any  dust,  colors 
are  revived,  while  the  fabric  sustains  no  injury  whatever. 
Carpets  of  any  description,  cloth,  and  other  like  materials  can 
be  similarly  cleaned  by  this  process. 

The  American  Pneumatic  Carpet-Cleaning  Company  has 
plants  located  in  New  York  City,  Chicago,  Boston,  Philadel- 
phia, Pittsburg,  and  Cincinnati. 


Chapter  XXIX. 


PNEUMATIC  WORK— Continued 


PNEUMATIC    WORK. 

{Continued.) 

COMPRESSED     AIR     IN     THE     BESSEMER     CONVERTER     AND     THE 

BLAST    FURNACE. 

In  no  other  industry  is  the  use  of  compressed  air  so  impor- 
tant a  factor  as  in  the  manufacture  of  iron  and  steel.  The  blast 
furnace  stands  first  in  estimation  with  its  vast  volumes  of  air 
at  varying  pressures  up  to  lo  pounds  or  more 
per  square  inch,  and  extending  in  pressure  up  to 
75  or  lOO  pounds  in  operating  the  Bessemer  con- 
verter, and  in  the  lifts  and  cranes  necessary  in 
the  modern  methods  in  steel  manufacture. 

The  Bessemer  converter  and  its  adjuncts 
require  the  most  precise  and  delicate  handling 
of  compressed  air  of  any  air  power  in  the  manu- 
facturing arts.  A  slight  mistake  in  handling 
the  air  valves,  or  in  blowing  the  melted  iron  to 
the  exact  degree  to  convert  it  into  steel,  may  involve  large 
costs,  if  not  disaster. 


Fig.  478.  —  BES- 
SEMER CONVERT- 
ER. 


THE    USE    OF   COMPRESSED    AIR   AT    A    BLAST-FURNACE    PLANT. 

When  "  A"  Furnace  of  the  Maryland  Steel  Company,  Spar- 
row's Point,  Md.,  was  blown  in  for  its  second  blast  (November, 
1895),  a  compressed-air  plant  was  put  in,  and  has  been  used 
with  much  success  during  the  past  years.  Compressed  air  is 
used  for  the  tap-hole  drill,  the  tap-hole  "gun,"  the  transfer 
table  at  the  scales,  the  turn-table  on  top  of  the  furnace,  and  for 
lifting  the  rails  of  the  turn-table  in  running  off  the  empty  cars. 

The  tap-hole  drill  is  a  Little  Giant  rock  drill  so  mounted  as 
to  swing  into  place  and  drill  out  the  tap-hole  without  any  hard 


664  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

manual  labor.  This  arrangement  is  the  device  of  Superin- 
tendent David  Baker,  and  is  described  by  him  in  Trans.  Aiiicr. 
Inst.  Min.  Eng.  (vol.  xxi.)  The  supporting  crane  has  been  much 
changed  since  that  description  was  written,  and  now  consists  of 
a  simple  and  light  crane.  The  crane  is  fastened  to  one  of  the 
columns  at  the  side  of  the  tap-hole  so  that  the  drill  can  be 
swung  back  out  of  the  way  when  not  in  use.  The  air-pipe  is 
connected  by  swing  joints  and  an  expansion  sleeve. 

Formerly  steam  was  used  to  run  the  drill,  but  it  has  several 
disadvantages  which  air  has  not.  Great  care  had  to  be  taken 
to  prevent  the  condensed  steam  from  dripping  into  the  iron 
trough  and  perhaps  causing  a  "boil."  The  escaping  steam 
would  make  it  hot  for  the  men,  and  the  clouds  of  vapor  would 
often  prevent  them  from  watching  the  work  well.  A  hose  for 
the  exhaust  was  necessary,  and  this  made  another  part  to  care 
for,  and  it  was  sometimes  burned.  In  cold  weather  there  would 
be  much  condensing  and  loss  of  power.  Compressed  air  does 
away  with  all  these  difficulties. 

The  tap-hole  gun  is  S.  W.  Vaughen's  patent  device  for  shut- 
ting the  tap-hole  by  power,  thus  saving  much  hard,  hot  work 
for  the  men,  and  doing  away  with  the  necessity  of  taking  the 
blast  off  the  furnace  after  each  cast  to  shut  the  tap-hole. 

The  gun  has  a  breech  for  loading,  a  compact  valve,  and  a 
simple  and  adjustable  mounting.  It  is  made  of  cast  iron  and 
consists  of  two  cylinders  and  a  piston  rod  with  a  piston  on  each 
end.  The  air  end  of  the  gun  is  an  ordinary  air-cylinder  oper- 
ated by  a  hand-valve.  The  clay  barrel  is  open  at  the  nose  end, 
and  has  a  breech  at  the  other  end.  The  gun  is  suspended  on  a 
crane  fastened  to  a  column  opposite  the  drill.  The  crane  is 
similar  to  the  drill  crane,  and  the  air-pipe  has  swing  joints  and 
a  rubber-hose  connection  to  allow  freedom  of  motion. 

The  gun  is  loaded  with  about  thirty-five  clay  balls  before 
the  cast,  and  when  the  iron  is  all  out  of  the  furnace  the 
gun  is  swung  around  and  clamped  into  place  and  the  whole 
charge  shot  into  the  tap-hole  at  once.     By  reversing  the  valve 


PNEUMATIC    WORK.  665 

the  piston  is  brought  back;  the  breech  is  opened,  the  clay  barrel 
loaded  np  again,  and  more  clay  shot  into  the  hole  till  it  is  com- 
pletely shut  up. 

Here  the  air  has  the  same  advantages  over  steam  as  in  the 
drill.  About  65  to  70  pounds  air  pressure  is  needed  for  the 
drill  and  gun.  If  at  any  time  there  is  not  enough  pressure  to 
run  the  drill  well,  a  signal  is  given  from  the  furnace  to  the 
pump-man,  and  he  sets  the  escape  valve  of  the  receiver  for 
higher  pressure. 

In  order  to  have  rapid  handling  of  the  ore,  limestone,  and 
coke,  buggies  are  used,  which  have  four  wheels,  run  on  tracks, 
and  hold  from  1,500  to  2,300  pounds  of  stock,  at  the  scales:  a 
transfer  table  is  placed  between  the  scales  and  the  elevator, 
which  is  operated  by  compressed  air  taken  from  the  blast  main 
air-pipe  at  lo  to  12  pounds  pressure. 

COMPRESSED    AIR    IN   A    ROLLING-MILL. 

Most  of  the  more  successful  iron-working  establishments 
now  use  "compressed  air"  a  little — some  a  great  deal;  and 
among  the  foremost  of  the  latter  class  is  the  Passaic  Rolling- 
Mill  Company  at  Paterson,  N.  J.,  not  only  because  of  its  ex- 
tensive use  of  compressed  air,  but  particularly  by  reason  of  the 
variety  of  operations  performed  by  it,  several  of  which  are  of 
more  than  ordinary  interest  and  originality. 

First  a  row  of  jib  cranes,  each  equipped  with  independent 
air  hoist,  used  for  loading  the  finished  material  on  cars  for 
shipment.  The  air  cylinders  for  this  work  are  about  6  inches 
diameter  by  6  feet  stroke,  mounted  on  the  mast,  the  air  con- 
nection being  made  with  a  short  piece  of  hose  at  the  top  of  the 
crane. 

One  of  the  most  interesting  applications  of  compressed  air, 
one  in  which  work  formerly  required  the  services  of  thirteen 
men,  is  now  done  by  four,  and  with  less  danger.  By  it  the 
capacity  of  the  rolls  has  been  trebled.     This  apparatus  is  not 


666  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

Operated  entirely  by  compressed  air,  steam  and  air  being  as- 
signed to  the  work  for  which  each  is  considered  best  suited. 
It  consists  of  two  transfer  tables,  one  on  each  side  of  the  main 
rolls  of  the  rolling  mill,  the  duty  of  one  of  which  is  to  deliver 
the  heated  billet  to  the  first  roll,  move  into  position  to  receive 
it  from  the  second,  move  and  deliver  it  to  the  third,  and  so  on 
till  the  billet  comes  out  a  finished  beam.  Of  course  the  process 
described  applies  to  the  table  on  one  side  of  the  rolls  only,  the 
one  on  the  opposite  side  operating  in  the  same  w^ay  with  it. 
This  transfer  table  consists  of  a  heavy  four-wheeled  carriage 
carrying  a  tilting  platform  or  girder,  the  top  of  which  consists 
of  rollers  operated  in  either  direction  by  bevel  gears  and  shaft. 
The  carriage  travels  in  the  pit  on  rails  parallel  to  the  rolls  in 
moving  from  one  roll  to  the  next,  and  the  end  of  the  tilting 
table  next  the  rolls  is  raised  and  lowered  to  position  for  the 
upper  and  lower  rolls  by  an  1 8-inch  air  cylinder  located  in  a 
yoke.  The  cross-bend  is  connected  at  its  centre  to  the  piston 
of  this  air  cylinder  and  moves  the  tilting  platform  by  means  of 
the  side  rods  fastened  to  its  ends.  The  action  of  this  cylinder 
is  controlled  by  a  special  valve,  operated  from  the  engineer's 
platform.  One  engineer  and  a  roll-tender  are  all  that  are  re- 
quired for  the  apparatus,  and  the  same  number  for  the  other 
table  on  the  opposite  side. 

After  the  beam  leaves  the  rolls  it  passes  to  the  hot  saw, 
where  it  is  trimmed  and  cut  to  length.  The  rollers  that  carry 
the  beam  to  the  saw  receive  it  from  the  rollers  on  the  transfer 
table,  without  any  handling  or  even  a  pause  in  its  motion,  so 
that  a  few  seconds  after  it  has  received  its  last  squeeze  in  the 
rolls  it  is  being  cut  by  the  saw.  This  saw  is  fed  through  the 
beam  by  a  compressed-air  cylinder,  which  is  12  inches  diameter 
by  20  inches  stroke ;  the  elastic  yet  persistent  nature  of  the 
feed  given  the  saw  by  compressed  air  is  found  much  better  than 
any  other  method. 

Compressed  air  performs  the  next  operation  on  the  beam, 
which  is  to  remove  it  from  the  rollers  (making  room   for  the 


PNEUMATIC    WORK.  667 

next)  and  set  it  on  edge  to  cool.  When  the  beam  lies  on  the 
rollers  after  being  cut  to  length  the  fingers  are  in  a  horizontal 
position  under  it  between  the  rollers,  and  an  air  cylinder,  15  x 
26  inches,  located  under  the  rollers,  pulls  the  fingers  to  a  vertical 
position,  bringing  the  beam  with  it,  at  the  same  time  carrying 
it  sideways  far  enough  to  clear  the  rollers. 

The  rest  of  the  work  done  by  air  in  these  works  is  being 
done  in  many  places  elsewhere,  and  is  consequently  of  but  pass- 
ing interest.  There  is  a  busy  corner  in  the  bridge  shop — a 
group  of  three  riveters,  two  reamers,  a  chipping  tool  and  hoist, 
all  being  operated  by  compressed  air.  The  total  pneumatic 
equipment  of  the  works,  outside  of  the  special  apparatus  de- 
scribed, consists  of  about  40  cylinder  hoists,  12  riveters,  5  drills 
and  reamers,  and  2  chipping  tools.  There  is  also  a  very  inter- 
esting device  for  charging  the  heating  furnace  by  compressed 
air. 

COMPRESSED   AIR   FOR   BLASTING   COAL. 

In  endeavoring  to  dispense  with  the  use  of  gunpowder  and 
other  asphyxiating  explosives  in  the  deep  drifts  of  coal  mines, 
a  series  of  experiments  were  made  in  the  colleries  at  Wigan 
and  Denton,  England,  a  number  of  years  since,  in  which  air 
was  compressed  to  946  atmospheres  over  14,000  pounds  per 
square  inch,  and  conveyed  in  strong  wrought-iron  tubes  to  a 
cast-iron  cartridge  placed  in  a  drill  hole  and  tamped  like  a  pow- 
der cartridge.  The  breaking  strain  of  the  cast-iron  cartridges 
by  comparative  tests  was  first  ascertained  to  obtain  the  proper 
size  and  thickness,  that  they  might  burst  at  or  near  some  assigned 
pressure,  say  10,000  pounds  per  square  inch.  Cored  castings 
could  not  be  used,  or  failed  from  the  drifting  of  the  core,  caus- 
ing weakness  on  one  side,  so  as  to  vitiate  many  of  the  experi- 
ments. A  size  of  drilled  and  turned  cartridges  was  adopted,  12 
inches  long,  3^^-  inches  diameter,  with  walls  3%  inch  thick,  hav- 
ing a  bore  i|f  inches  diameter.  This  was  found  to  burst  at 
9,500  pounds  per  square  inch  pressure.      These  air  cartridges 


668  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

were  pushed  into  close-fitting  bores  in  the  undercut  coal  wall  with 
a  small  pipe  attached  and  tamped  the  same  as  with  a  gunpowder 
cartridge ;  the  small  air  pipe  was  laid  to  a  safe  distance  to  a  re- 
ceiver charged  at  a  much  higher  pressure,  when  on  opening  a 
valve  the  compressed  air  rushed  to  the  cartridge  and  an  explo- 
sion occurred  much  in  effect  like  other  explosives,  and  throwing 
down  a  wall  face  of  from  5  to  6  tons  at  each  blast.  The  air 
compressor  placed  at  the  power  station  readily  compressed  the 
air  to  the  required  pressure,  which  was  transmitted  to  strong 
receivers  near  the  working  heads,  where  the  operation  of  charg- 
ing a  receiver  and  a  cartridge  was  readily  done  by  the  high- 
pressure  valves  at  the  receiver.  In  this  manner  the  miners 
could  carry  on  the  work  constantly  without  having  to  retire 
from  the  influence  of  deleterious  gases,  and  had  only  to  momen- 
tarily shield  themselves  from  flying  coal.  The  ventilating  and 
cooling  properties  of  air  thus  used  cannot  be  too  highly  praised 
as  one  of  the  safeguards  in  the  dangerous  work  of  mining  coal 
in  the  deep  and  gas-saturated  workings  of  the  bituminous  coal 
belts. 

Although  the  expense  of  blasting  by  compressed  air  was 
found  somewhat  greater  than  by  the  use  of  powder  or  dynamite, 
this  system  was  proved  feasible,  but  was  not  continued.  It  is 
assumed  that  compressed  air  yet  stands  foremost  as  a  substitute 
for  the  dangerous  explosives  heretofore  used,  by  the  increasing 
depths  at  which  safety  is  a  paramount  requirement. 

THE   AIR-LOCK   SYSTEM    IN    CAISSON   SINKING. 

One  of  the  latest  improvements  in  the  use  of  compressed  air 
in  sinking  the  foundations  for  buildings  is  the  air  lock,  of  which 
the  outside  feature  is  illustrated  in  Fig.  479.  It  consists  of  a 
large  steel  case  or  chamber  containing  the  air-lock  mechanism ; 
a  neck  extending  down  a  few  feet  and  fixed  to  the  top  of  the 
wooden  caisson  by  a  flange;  a  platform  at  the  top  as  a  footing 
for  the  men  operating  the  caisson  valves,  and  the  hoisting  of  the 


THE   AIR-LOCK    SYSTEM    IN    CAISSON    SINKING. 


669 


excavated  material.  This  system  enables  an  ordinary  bucket, 
or  even  a  barrel  of  cement,  to  be  passed  in  and  out  of  the  cais- 
son without  detaching  it  from  the  hoisting-rope  leading  to  the 
derrick.  The  lock  has  a  simple  lower  door  hinged  on  a  shaft, 
which  shaft  extends  to  the  outside  of  the  lock  through  a  stuf- 
fing box.  On  the  outside 
is  a  counter  weight  lever 
and  counter-weight,  to  bal- 
ance the  door  and  afford 
means  of  operating  from 
the  outside.  Above  the 
lower  door  is  a  cylindrical 
section,  called  the  bucket 
chamber,  large  enough  to 
contain  the  bucket.  The 
opening  above  the  bucket 
chamber,  instead  of  being 
closed  by  a  single  door,  is 
closed  by  two  doors  work- 
ing to  and  from  the  centre. 
When  these  doors  are 
shut  they  completely  close 
the  opening,  and  form 
a  tight  joint  with  each 
other,  with  the  exception 
of  a  small  opening  at  the 
centre.  In  this  small 
opening  at  the  centre  fits 
a  stuffing-box  of  simple 
design,  through  which  the  hoist-rope  passes.  The  two  doors 
then  close  around  the  rope  contained  in  the  stuffing-box  and 
completely  prevent  the  escape  of  air  through  the  opening, 
while  permitting  the  rope  to  pass  freely.  As  soon  as  the  bucket 
is  filled  in  the  working  chamber  an  electric  bell  rings  above, 
and  the  engineer  at  the  derrick  hoists  the  bucket  into  the  bucket 


Fig.  479.— the  air  lock. 


670 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


chamber.  The  lower  door  is  then  closed,  a  valve  is  opened 
permitting  the  air  in  the  lock  to  escape,  the  upper  doors  are 
then  opened,  and  the  bucket  is  hoisted  out, 
the  stuffing-box  remaining  on  the  rope  just 
above  the  bucket.  In  returning,  the  opera- 
tions are  reversed. 

The  caisson  is  an  excavating  machine,  as 
well  as  a  foundation,  and  must  be  considered 
in  that  light. 

The  side  elevation  (Fig.  480)  shows  the 
air  lock  at  the  top,  with  the  levers  L  L  '  and 
their  counter-weights  JV  JV\  below  which  is 
the  elevator  or  air  shaft,  with  the  ladder,  as 
shown,  and  at  the  extreme  lower  part  is  the 
air  chamber.  The  openings  J/  and  Xare  re- 
spectively for  the  air  pipe  and  the  w^histle  con- 
nection, as  shown  in  the  cut  Fig.  480.  The 
illustration  Fig.  481  gives  the  details  of  the 
internal  arrangement. 

Referring  to  Fig.  481,  the  upper  swinging 

gates,    A   and   A',    turn    about  the  centre,  O, 

being  counterweighted  by  Fand  F'.     These 

■■  .       are  worked  by  the  handle  L,  both  gates  swing- 

p  11      ing  on  the  centres  D  and  //. 

When  the  upper  gates  have  been  moved 
to  the  open  position,  so  as  to  come  at  rest  on 
the  lugs  B  and  B',  the  buckets  can  be  moved 
in  or  out  of  the  air  chamber.  The  meeting 
edges  of  these,  as  well  as  the  lower  gates, 
are  packed  with  rubber  tongues,  so  as  to  make 
air-tight  closures.  The  lower  swinging  gates 
are  worked  in  the  same  manner,  being  opened  and  closed  by 
the  lever  L  \  and  counterweighted  by  IV  (Fig.  480). 

The   successive   operations  are   as  follows:    The  bucket   is 
lowered  into  the  air  lock,  the  upper  gates  being  open  and  the 


Fig.  480.— side  view. 


THE    AIR-LOCK    SYSTEM    IN    CAISSON    SINKING. 


671 


Hoisting  Cable 

^^4 


Rubber  Packing 
ji'  ^PP^^  Sieinging 
"  -\— — n  Gates 


lower  ones  closed.  The  upper  ones  are  then  closed  and  air  is 
admitted  from  the  air  shaft  until  the  pressure  equals  the  press- 
ure in  the  air  chamber.  The  lower  gates  are  then  opened  and 
the  bucket  descends  into  the  shaft  and  finally  into  the  caisson 
chamber. 

There  is  a  three-way  valve,  which  serves  three  purposes: 
First,  it  permits  air  to  escape  from  the  air  lock ;  second,  it 
equalizes  the  pressures  in  the  air 
chamber  and  the  air  lock,  and, 
third,  it  prevents  the  escape  of  air 
from  either.  It  is  regulated  by 
means  of  contact  wheels,  which  in 
turn  are  moved  by  connecting  with 
the  handle  L  by  means  of  a  rod 
not  shown  in  the  figures.  When 
the  upper  gates  are  closed  the 
motion  of  the  lever  simultaneously 
closes  the  air  exhaust  from  the 
air  lock  and  makes  connection 
with  the  air  chamber  below,  thus 
equalizing  the  pressure  in  the  two 
chambers.  A  thumb-latch  locks 
these  doors  in  both  the  open  and 
in  the  closed  position.  The  ar- 
rangement of  the  lower  swinging  gates  prevents  their  move- 
ment until  the  pressures  in  the  upper  and  lower  chambers  have 
been  equalized. 


5jP  '  Lower  Swinging  Gates    jm 
li  n 

Fig.  481.— air-lock  chamber 


Chapter  XXX. 


THE   PNEUMATIC  SYSTEM 
OF  TUBE  TRANSMISSION 


673 


THE    PNEUMATIC   SYSTEM    OF   TUBE 
TRANSMISSION. 

The  earliest  suggestion  and  experiment  in  the  work  of 
transmission  in  tubes  was  made  by  Dr.  Papin  in  the  seven- 
teenth century,  since  which  its  usefulness  lay  dormant  through 
the  centuries  until  1853,  when  the  first  successful  pneumatic- 
tube  system  was  put  in  operation  in  London,  England,  with  a 
i^-inch  tube  650  feet  long.  It  was  operated  by  a  vacuum  and 
again  extended  in  1858  with  2^-inch  tubes.  From  this  on,  the 
system  has  grown  rapidly,  and  London  has  34  miles  of  despatch 
tubes  with  42  stations;  the  transmission  power  being  by  both 
compression  and  exhaustion.  It  has  also  extended  its  useful- 
ness in  the  large  cities  of  England  and  on  the  Continent.  In 
Berlin,  Germany,  the  transmission  of  telegraph  messages  by 
pneumatic  tubes  commenced  in  1865.  There  is  quite  an  inter- 
esting history  of  the  experiments  in  transmission  of  passengers 
and  goods  by  this  system,  covering  many  years  of  trial,  but,  as 
it  has  not  proved  successful,  we  pass  it  by.  Its  most  success- 
ful score  is  in  the  store  cash  system,  the  telegraph  despatch, 
and  the  later  postal-transfer  system. 

Its  first  introduction  on  the  larger  scale  was  made  in  Phila- 
delphia in  1893.  A  six-inch  main  was  laid  to  connect  the  main 
post-office  with  the  Chestnut  Street  branch,  a  distance  of  nearly 
a  mile. 

On  account  of  the  large  size  of  the  pipes  compared  to  those 
used  in  the  European  system,  the  capacity  of  this  plant  was 
much  greater.  The  area  of  the  tubes  was  increased  many 
times,  and  of  course  the  carriers  were  correspondingly  larger. 
The  speed  of  the  Philadelphia  system  was,  moreover,  doubled, 
and  it  had  improved  appliances  for  receiving  and  transmitting. 


676  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

This  plant  was  opened  in  1893  and  has  been  operated  success- 
fully ever  since. 

The  air  current  flows  continuously  from  the  main  post-office 
to  the  Bourse  through  one  tube  and  returns  to  the  main  post- 
office  through  the  other,  thus  forming  a  loop  with  the  return 
end  connected  to  the  suction  pipe  of  the  compressor  at  the  post- 
office.  There  is  an  opening  in  the  tube  to  the  atmosphere  near 
where  it  is  connected  to  the  compressor,  so  that  the  entire  cir- 
cuit contains  air  at  a  pressure  above  the  atmosphere.  It  is  a 
pressure  system  rather  than  a  vacuum  system,  as  these  terms 
are  commonly  understood. 

Carriers  occupy  sixty  seconds  in  transit  from  the  post-office 
to  the  Bourse,  and  fifty-five  seconds  for  the  return  trip.  The 
carrier  is  only  18  inches  long;  but  each  carrier  has  a  capac- 
ity of  200  letters,  and  they  can  be  despatched  at  six-second 
intervals,  making  the  tube  capacity  240,000  letters  per  hour, 
including  both  directions.  The  actual  speed  in  practice  is  about 
52  feet  per  second,  in  the  Philadelphia  service,  and  in  the  first 
four  years  it  was  in  use  it  is  estimated  that  more  than  35,000,- 
000  letters  were  despatched  through  these  tubes,  with  but  one 
serious  interruption  due  to  an  obstruction  in  the  tubes. 

It  was  determined  for  the  New  York  system  to  make  the 
tubes  of  larger  capacity  than  those  used  in  Philadelphia,  and  to 
maintain  a  working  speed  of  thirty  miles  an  hour  under  a  head- 
way of  twelve  seconds.  The  line  to  the  Produce  Exchange  is 
nearly  4,000  feet  long  and  consists  of  two  tubes,  side  by  side, 
8  inches  in  diameter,  and  about  5  feet  below  the  surface.  One 
is  used  for  outgoing  and  the  other  for  incoming  mail,  they  being 
connected  at  the  sub-station  by  a  loop.  A  powerful  compressor 
forces  the  air  into  the  outgoing  tube  at  a  pressure  of  7  pounds 
to  the  square  inch.  On  account  of  its  elasticity,  it  flows  through 
the  pipe  with  an  increasing  velocity,  but  by  the  time  it  reaches 
the  sub-station  the  pressure  has  fallen  just  one-half.  From 
here  the  current  returns  by  the  second  or  return  tube,  and  as  it 
enters  the  receiving  tank  its  pressure  is  equal  to  that  of  the 


THE    PNEUMATIC    SYSTEM    OF   TUBE   TRANSMISSION. 


^77 


atmosphere.  This  tank  is  joined  to  the  suction  pipe  of  the 
compressor,  and  as  the  two  lines  are  connected  by  a  loop  at  the 
other  end,  there  is  a  continual  circulation  of  air  throughout. 
The  pipes  are  of  cast  iron  with  a  very  smooth  interior  finish. 
All  bends  are  of  at  least  8-feet  radius  and  made  of  seamless 
brass  with  a  diameter  of  not  less  than  8f  inches  on  the  inside. 

The  current  is  continuous  from  the  starting  of  the  compres- 
sors in  the  morning  until  they  stop  at  night,  so  it  was  necessary 
to  have  some  means  by  which  the  carriers  could  be  inserted  and 
removed  from  the  line  without  interfering  with  the  flow  of  air. 
This  is  done  by  means  of  a  transmitter  and  receiver,  one  at 


Fig.  482.— sending  apparatus  and  receiver,  new  york  post-office. 


each  station.  The  former  consists  of  a  piece  of  8-inch  pipe, 
long  enough  to  enclose  the  carrier.  It  is  hung  on  a  shaft,  over- 
head, so  that  it  can  be  swung  out  from  the  main  line  to  receive 
the  carrier  and  then  moved  back  into  position  where  the  current 
forces  the  latter  into  the  main  tube.  The  ends  are  smoothed 
off  square  so  that  no  air  can  escape  at  the  joints.  When  this 
section  is  swung  out  of  line  two  projecting  plates  move  across 
the  ends  of  the  opening  and  shut  off  the  air,  the  current  mean- 
while going  around  by  means  of  a  connection.  When  the  trans- 
mitter is  not  in  use  the  movable  section  is  drawn  over  to  the 
loading  tray  and  the  air  goes  through  the  U-shaped  by-pass. 
When  a  carrier  is  to  be  sent  it  is  placed  in  the  tray  and  pushed 


6/8 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


into  the  transmitter;  tiien,  by  pulling  a  lever,  the  latter  is 
swung  into  position  and  the  carrier  is  forced  out.  An  automatic 
time-lock  prevents  them  being  sent  with  less  than  twelve  sec- 
onds headway,  thus  insuring  a  proper  distance  between  them 
in  the  tube.  When  the  carriers  arrive  at  the  sub-station  the 
pressure  of  the  air  is  3^  pounds  to  the  square  inch,  so  the  tube 
cannot  be  opened  to  remove  them.  They  also  have  a  velocity 
of  about  thirty  miles  an  hour,  and  some  means  had  to  be  pro- 
vided for  gradually 
checking  their  speed. 
These  two  things  are 
accomplished  by  means 
of  a  closed  receiver, 
which  consists  of  an  8- 
inch  cylinder  4  feet  in 
length.  In  its  normal 
position  it  forms  a  con- 
tinuation of  the  tube  by 
which  the  carrier  ar- 
rives, and  on  entering 
the  receiver  it  com- 
presses the  air  in  front 
and  is  stopped  without 
any  shock.  There  are 
a  number  of  openings  in  the  pipe  just  in  front  of  the  receiver 
connected  with  the  other  or  returning  line  by  which  the  current 
continues  back  to  the  main  station.  The  compressed  air  in  the 
receiver  opens  a  small  valve  and  thus  keeps  the  carrier  from 
being  thrown  back  into  the  main  tube.  The  receiver  is  auto- 
matically discharged  in  three  or  four  seconds  by  a  piston,  which 
tilts  it  to  an  angle  of  40°.  The  carrier  slides  out  onto  an  in- 
clined platform  which  is  kept  in  position  by  a  counter-weight. 
The  weight  of  the  carrier,  however,  overbalances  this  and 
causes  it  to  drop  to  a  horizontal  position,  and  the  carrier  is 
thrown  out  on  to  a  table  in  front  of  the  operator.     This  piston 


Fig.  483- 


-SENDING      APPARATUS      AND     CLOSED     RE- 
CEIVER  AT   A  STATION. 


THE    PNEUMATIC    S\\STExM    OF   TUBE    TRANSMISSION. 


679 


is  worked  by  compressed  air  supplied  from  the  receiver.  Above 
the  front  end  of  the  receiving  chamber  is  a  plate,  arranged  so 
that  it  comes  down  and  closes  the  end  of  the  main  tube  when 
the  receiver  is  tilted  to  be  discharged. 

The  transmitters  at  both  ends  of  the  line  are  the  same,  but 
the  receiver  at  the  main  office  is  different  from  the  one  at  the 
sub-station.  At  this  end  it  consists  of  a  section  of  the  end  of 
the  tube  closed  at  the  rear  by  a  gate.     The  air,  now  expanded 


Fig.  4S4.— section  of  sending  apparatus. 

to  the  same  pressure  as  the  atmosphere,  passes  from  the  tube 
through  openings,  four  feet  in  front  of  the  receiver  gate,  down 
to  the  tank  in  the  basement.  The  momentum  of  the  carrier  is 
checked  in  compressing  the  air  in  the  chamber  after  it  has 
passed  these  openings.  Part  of  this  compressed  air  operates  a 
piston  which  opens  the  gate  mentioned  above,  then  the  small 
pressure  of  air  forces  the  carrier  out  on  to  the  receiving  table. 
If  there  is  not  sufficient  pressure  to  expel  it,  the  openings  can 
be  partly  closed  by  means  of  a  valve.  As  it  passes  out,  it  hits 
a  small  finger  which  causes  the  gate  to  be  closed. 

Intermediate    stations    are    usually    supplied    with    cut-out 


68o  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

switches,  so  that  carriers  can  be  sent  directly  past  the  station 
without  entering  it.  These  switches  are  moved  by  air  pressure, 
controlled  electrically  from  the  nearest  station  (see  Fig.  485). 

There  is  no  part  of  this  system  that  has  been  the  object  of 
more  thought  and  study  than  the  carrier  that  contains  the  mail 
or  other  material  to  be  transported.  It  is  made  of  a  seamless 
steel  tube  23!  inches  long,  closed  at  the  front  end  by  a  sheet 
metal  head  and  buffer,  and  closed  at  the  rear  end  by  a  hinged 
cover  provided  with  a  lock  (see  Fig.  486).  The  right-hand 
carrier  is  of  the  New  York  system. 

The  body  of  the  carrier  is  about  an  inch  smaller  than  the 
tube  through  which  it  travels,  the  space  between  the  body  of 


Fig.  485.— cut-out  switches  from  main  line. 

the  carrier  and  the  surface  of  the  tube  being  filled  by  two 
fibrous  rings  that  serve  not  only  to  prevent  the  escape  of  air 
past  the  carrier,  but  as  wearing  surfaces  to  slide  on  the  lower 
side  of  the  tube.  These  bearing  rings  are  made  of  cotton  fibre, 
and  they  will  endure  until  the  carrier  has  travelled  about  5,000 
miles,  when  they  become  worn  so  small  that  they  have  to  be 
replaced  by  new  ones.  A  carrier  weighs  I3f  pounds  and  will 
contain  600  ordinary  letters. 

In  Fig.  486  is  represented  the  comparative  sizes  of  the  car- 
riers   used   in   the   progress  and   expansion   of  the   pneumatic 


THE    I'XEUMATIC    SYSTEM    OF   TUBE   TRANSMISSION, 


68 1 


transmission  system.  Xo.  i  to  the  left  is  the  carrier  used  in 
the  Berlin  system;  No.  2,  the  largest  carrier  used  in  the  Lon- 
don system ;  No.  3,  a  six-inch  carrier  of  the  Philadelphia  sys- 
tem ;  No.  4,  an  eight-inch  carrier  of  the  New  York  and  Boston 
systems.  No.  2  is  also 
the  comparative  size  of 
the  New  York  telegraph 
despatch  system. 

LOCATION  OF  OBSTRUC- 
TIONS BY  LODGMENT  OF 
A   CARRIER. 

Considerable  appre- 
hension arose  from  the 
accidental  lodgment  of  a 
carrier  in  the  Philadel- 
phia tube,  and  also  later 
in  the  New  York  and 
Brooklyn  post-oiBce  line. 

The  plan  was  to  disconnect  the  terminal  apparatus  at  one 
of  the  stations,  fire  a  pistol  into  the  tube,  and  note  the  time 
that  elapsed  between  the  discharge  of  the  pistol  and  the  return 
of  the  sound  as  an  echo  reflected  back  from  the  obstructing 
carrier;  then,  knowing  the  velocity  of  sound,  a  simple  calcula- 
tion would  give  the  distance  from  the  station  to  the  carrier. 

A  chronograph  improvised  for  registering  the  time  consisted 
in  part  of  a  metal  cylinder  or  drum  10  inches  in  diameter,  which 
could  be  revolved  by  a  hand  crank  and  which  would  move  end- 
wise very  slowly  when  in  rotation.  The  polished  metal  surface 
was  coated  with  smoke,  and  therefore  a  motionless  pin-point, 
in  contact  with  the  drum,  would  trace  a  fine  spiral  line  thereon. 
The  point  was  not  motionless,  though.  It  was  attached  by  a 
horsehair  and  sealing-wax  to  one  prong  of  a  tuning-fork  giving 
the  musical  note  C,  and  therefore  vibrating  512  times  per  sec- 
ond.    Consequently  512  waves  per  second  were  imparted  to  the 


Fig.  4S6.— the  carriers. 


682  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

trace ;  and  these  were  large  enough  to  admit  of  division  into 
quarters.  Another  disturbance  of  the  point  was  caused  elec- 
trically by  a  pendulum  of  a  clock  beating  half-seconds.  Each 
beat  made  a  short,  sharp  projection  sideways  on  the  wavy  line. 
Hence,  the  complete  half-seconds  could  be  counted  by  these 
marks,  while  the  time  interval  remaining  after  the  last  pendu- 
lum beat  could  be  ascertained  from  the  tuning-fork  waves. 

Finally,  provision  was  made  for  automatically  recording  on 
the  cylinder  the  instant  of  the  original  shot  and  also  of  the 
arrival  of  the  echo.  A  vibrating  diaphragm  close  to  the  drum 
bore  another  stylus  or  sharp  point,  and  this  diaphragm  was  so 
sensitive  that,  when  struck  by  sound,  it  would  move  enough  to 
make  a  scratch  on  the  sooty  surface. 

Five  trials  were  made  with  this  apparatus,  and  the  mean  of 
the  observations  gave  2.793  seconds  as  the  time  required  for 
the  sound  to  travel  both  ways.  A  velocity  of  1,093  feet  was 
assumed  for  a  temperature  of  32°,  and  a  correction  of  1.12  feet 
per  second  for  each  degree  above  that  standard  was  applied. 
The  observed  temperature  down  in  the  ground  was  39°.  The 
computed  velocity  was  1,101  feet,  and  the  estimated  distance, 
counting  both  ways,  was  therefore  3,075  feet.  Dividing  by 
two,  the  explorers  made  the  actual  distance  of  the  box  1,537  feet 
from  the  open  end  of  the  tube.  This  was  more  than  a  quarter 
of  a  mile  off.  When  workmen  dug  down  at  the  designated 
spot,  several  blocks  away,  they  found  the  box  within  a  foot  or 
two  of  the  place.  A  break  had  occurred  in  the  pipe  about 
twenty  feet  further  away,  but  the  obstruction  was  found  exactly 
where  calculation  located  it. 

THE    ENGLISH    TUBE    SYSTEM. 

Sorne  computations  have  been  made  by  English  experts  on 
the  power  required  to  operate  a  pneumatic-tube  system  of 
2^  and  3 -inch  tubes  which  is  applicable  to  the  larger  tubes  in 
the  ratio  of  their  comparative  areas. 

"The  pneumatic  tubes  used  in  Great  Britain  are  made  of 


THE    PNEUMATIC    SYSTEM    OF   TUBE    TRANSMISSION.  683 

lead,  and  when  laid  beneath  the  streets  they  are  enclosed  in 
iron  pipes  for  protection.  The  tubes  vary  in  length  from  two 
miles  downward,  the  average  length  being  about  three-fourths 
of  a  mile.  The  diameter  of  the  longer  and  more  important 
tubes  is  3  inches,  and  that  of  the  shorter  and  less  important 
tubes  2i  inches.  The  carriers  within  which  the  messages  are 
sent  through  the  tubes  are  made  of  gutta-percha  tubing,  cov- 
ered with  felt,  and  have  a  head  of  several  pieces  of  felt  which 
accurately  fits  the  tube.  The  carriers  used  with  the  3-inch 
tubes  weigh  about  7  ounces,  and  will  contain  about  thirty-six 
messages;  those  used  with  the  2i-inch  tubes  weigh  about  2^ 
ounces,  and  will  contain  about  twelve  messages. 

"  Each  of  the  tubes  is  provided  with  a  simple  electrical  con- 
trivance by  which  the  departure  from  and  the  arrival  at  each 
station  of  the  carriers  is  signalled, 

"  The  power  by  which  these  tubes  are  worked  is  derived 
from  steam  engines  located  at  the  central  office.  These  engines 
work  air  pumps  which  either  take  air  from  the  atmosphere  and 
compress  it  to  a  smaller  volume  and  then  discharge  it  into  the 
pressure  main,  whence  it  is  admitted  by  means  of  taps  into  the 
different  tubes  when  carriers  are  despatched  to  an  out-station — 
or  the  pumps  take  air  from  the  vacuum  main,  compress  it  to 
the  atmospheric  pressure,  and  then  discharge  it  into  the  atmos- 
phere; the  air  in  the  vacuum  main  is,  of  course,  being  contin- 
ually renewed  by  the  air  which  flows  from  the  atmosphere 
through  the  tubes  into  the  vacuum  mains  during  the  transit  of 
the  carriers  from  the  out-stations. 

"  The  velocity  with  which  the  carriers  travel  is  usually  be- 
tween one-third  and  one-half  a  mile  per  minute.  The  approxi- 
mate time  of  transit  in  minutes  through  a  tube  of  L  miles  = 
2.7  L3  with  the  2i-inch  tube,  and  2.1  L^  with  the  3-inch  tube. 

"  The  energy  expended  in  driving  a  carrier  from  the  cen- 
tral office  to  an  out-station  is  equal  to  the  volume  of  compressed 
air  which  flows  into  the  tube  during  the  transit  multiplied  by 
the  work  required  to  produce  a  unit  volume  of  compressed  air. 


684  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

"  The  volume  of  compressed  air  which  flows  into  the  tube 
during  transit  is  equal  to  about  six-sevenths  of  the  tube's  cubical 
capacity.  The  capacities  of  the  2^  and  3-inch  tubes  are  146 
and  251  cubic  feet  per  mile  respectively,  so  that  the  volumes  of 
compressed  air  used  in  driving  a  carrier  through  a  mile  of  each 
tube  are  125  and  200  cubic  feet  respectively. 

"  The  work  required  to  produce  a  cubic  foot  of  compressed 
air  at  a  pressure  Pi  from  a  pressure  p„  lies  between  the  isother- 
mal value 

0.01005  Pi  log-  —  horse-power  minutes,  (i) 

Po 

and  the  adiabatical  value 

0.01505  Pj  -;  fi-M      —  I   -  horse-power  minutes,  (2) 

So  that  to  produce  a  cubic  foot  of  compressed  air  at  a  press- 
ure of  12  pounds  to  the  square  inch  above  the  atmospheric 
pressure  would  require  between  0.0695  and  0.0755  net  horse- 
power minute,  or  say  about  0.085  gross  horse-power  minute; 
and,  therefore,  the  energy  expended  in  driving  a  carrier  through 
a  mile  of  the  2^  and  3-inch  tubes  would  be  10.6  and  17  horse- 
power minutes  respectively. 

"  When  a  carrier  is  despatched  from  an  out-station  to  the 
central  office,  the  air  in  the  tube  first  expands  into  the  vacuum 
main  and  thence  into  the  pumps,  where  it  is  compressed  to  the 
atmospheric  pressure  and  then  discharged  into  the  atmosphere. 
By  the  aid  of  formulae  1  and  2,  it  is  found  that  the  gross  amount 
of  work  of  0.065  horse-power,  minute  is  required  to  pump  a 
cubic  foot  of  air  into  the  atmosphere  from  a  vacuum  main  at  a 
pressure  of  8  pounds  per  square  inch  below  the  atmospheric 
pressure.  If  the  tube  has  been  at  rest  immediately  before  the 
carrier  is  despatched  to  the  central  office,  the  volume  of  air 
which  will  be  pumped  into  the  atmosphere  from  the  vacuum 
mains  will  be  equal  to  the  cubical  capacity  of  the  tube;  and, 
therefore,  the  energy  expended  in  the  transmission  of  the  car- 
rier would  be  8  and  13  horse-power  minutes  with  2^  and  3-inch 


THE    PNEUMATIC    SYSTEM    OF   TUBE   TRANSMISSION.  685 

tubes  respectively.  If,  however,  the  tube  had  immediately 
previously  been  used  to  receive  a  carrier  from  an  out-station, 
there  would  be  a  partial  vacuum  in  the  tube,  and,  therefore, 
the  expenditure  of  energy  would  be  less,  say  6i  and  loi  horse- 
power minutes  respectively.  But  if,  on  the  other  hand,  the 
tube  had  just  previously  been  used  to  despatch  a  carrier  to  an 
out-station,  it  would  be  partially  filled  with  compressed  air; 
and  the  amount  of  work  which  the  pumps  would  have  to  per- 
form would  be  greater,  and  the  amount  of  energy  expended 
during  the  transit  of  the  carrier  would  be  about  12  and  19  horse- 
power minutes  with  the  2^  and  3-inch  tubes  respectively. 

"  These  amounts  of  energy  would  be  expended  in  several 
different  forms.  First,  work  would  be  performed  in  pushing 
back  the  atmosphere  at  that  end  of  the  tube  at  which  the  press- 
ure was  lowest;  secondly,  energy  would  be  expended  in  gen- 
erating mechanical  vibrations  of  the  tube;  and,  thirdly,  in  over- 
coming the  friction  of  the  carrier  within  the  tube.  The  first  of 
these  quantities  is  much  the  greatest,  and  is  equal  to  about 
three-fourths  the  net  work  of  the  engine  in  pressure  working, 
or  about  two-thirds  the  net  work  of  the  engine  in  vacuum 
working. 

"  The  energy  expended  in  overcoming  the  friction  of  the 
carrier   may    be    approximately    calculated    from    the    formula 

■ horse-power  minutes,  where  W  is  the  weight  of  the  car- 

150 

rier  in  ounces  and  L  length  of  tube  in  miles. 

"Thus,  with  the  2i-inch  tube,  the  energy  expended  in  over- 
coming the  friction  of  the  carrier  through  a  mile  of  tube  would 
be  about  -^\  horse-power  minute,  or  with  the  3-inch  tube  about 
•^ijj-  horse-power  minute.  So  that  the  energy  expended  in  over- 
coming the  friction  of  the  carrier  itself  would  be  only  -^^  to 
■g^-g-  of  that  expended  in  expelling  the  air  from  the  tube." 

The  mail-tube  industry  has  now  developed  so  fast  in  this 
country  that  even  8-inch  tubes,  with  cartridges  carrying  six 
hundred  letters,  are  in  successful  operation  in  our  big  cities. 


C86 


COMPRESSED   AIR    AND    ITS    APPLICATIONS. 


The  longest  circuit  ever  built  in  the  world  is  in  the  main  line 
recently  laid  in  New  York  City,  extending  from  the  terminal 
post-office,  a  distance  of  three  and  one-half  miles.  This  is  an 
8-inch  tube  circuit.  The  cartridges  travel 
at  tremendous  speed,  the  time  of  transit 
consumed  in  either  direction  being  only 
seven  minutes.  Another  big  circuit  has 
been  laid  across  the  Brooklyn  Bridge,  so 
that  you  may  have  the  pleasure  of  knowing 
that  while  you  are  speeding  over  the  bridge 
in  the  cars,  your  mail  may  be  making  bet- 
ter time  ahead  of  you,  shooting  away  in 
the  cartridge  inside  the  big  tube  like  an 
8-inch  projectile. 


COMPRESSED 


AIR     IN     STORE 
SERVICE. 


AND     OFFICE 


The  pneumatic  lift  is  one  of  the  mod- 
ern conveniences  for  the  quick  transmis- 
sion of  packages  and  light  goods — in  fact, 
a  perfect  compressed-air  dumb-waiter  ser- 
vice for  our  high  buildings. 

There  are  five  air  lifts  in  TJic  World 
building,  one  of  which  runs  up  through 
the  entire  building,  by  which  an  immense 
business  is  transacted  in  transmitting  copy 
and  orders. 

As  will  be  seen  in  Fig.  487,  a  cylinder 

is  employed  which  is  equal  in  length  to  the 

range  of  motion   of  the  car.     On  account 

of  its  length  it  is  small  in  size,  and  can  be 

placed  in  the  elevator  well.     The  suspender 

rope  of  the  car  passes  directly  into  the  cylinder,  and  is  attached 

to  the  piston.     The  rigid  piston  is  thus  avoided,  and  therefore 

no  doubling    blocks   or    multiplying  gear  are  required.      The 


Fig.   487  —PARCEL  LIFT. 


THE    PNEUMATIC    SYSTEM    OF   TUBE   TRANSMISSION.  68/ 


'^'iiiam0> 


Fig.  488.— pneumatic  elevator  and  tube  transmission. 

For  stores  and  office  buildings.     Sj^stem  of  the  Miles  Pneumatic  Tube  Company, 
1223  Broadway,  New  York  City. 


688 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


piston  lifts  the  car  by  a  force  of  compressed  air  let  into  the 
cylinder  by  a  valve.  The  compressed  air  is  supplied  from  a 
pressure  tank,  automatically  regulated,  precisely  as  it  is  for  the 
operation  of  despatch  tubes.  Hence  a  system  of  tubes  and 
light  elevators  can  be  operated  from  the  same  pressure  tank. 

The  pneumatic  elevator  and  system  of  pneumatic-carrier 
tubes  converging  to  a  central  station  are  all  operated  from  the 
same  air-pump  and  receiver. 

In  this  system,  when  the  tubes  are  not  in  actual  use  making 


Fig.  4S9.— the  counter  station. 

transmissions,  they  are  open  at  both  ends  to  the  atmosphere, 
and  can  be  used  as  speaking-tubes.  They  are  in  use  in  some 
of  the  largest  buildings  in  our  cities,  notably  the  Waldorf- 
Astoria  Hotel.  Single  lines  are  in  use  1,200  feet  between  ter- 
minals. 

The  counter  station  (Fig.  489)  is  used  for  store  service  and 
office  counters,  showing  tube,  terminal,  and  metallic  hood.  The 
valve  is  released  by  an  electro-magnet,  which  throws  the  catch 
off  the  cover  and  is  operated  by  a  key  at  the  other  terminal. 

Fig.  490  shows  the  operating  mechanism  of  the  automatic 


THE    PNEUMATIC    SYSTEM    OF   TUBE    TRANSMISSION.  689 

terminal  valve  and  its  air-pressure  lock.  As  soon  as  the  car- 
rier is  expelled  from  the  tube,  the  closed  cover  automatically 
opens  to  the  position  shown 
in  the  valve  represented  on 
the  left-hand  side  of  the  cut. 
The  pressure  is  automatically 
shut  off  by  the  opening  cover, 
and  the  tube  is  then  open  at 
both  ends  to  the  atmosphere, 
and  stands  ready  to  transmit 
carriers  from  either  end  to  the 
other  end,  and  while  not  in 
actual  use  it  consumes  no 
power.  The  tube  can  open 
downwardly  at  the  ends,  or 
upwardly,  as  shov/n  in  the 
hand-operated  terminal  (Fig. 
491).  The  adjacent  connec- 
tion with  the  pressure-supply  pipe  is  opened  by  shutting  the 
cover,  and  automatically  is  held  open  while  the  cover  remains 


Fig.   490.— AUTOMAIIC  TEKMIXAL  VALVE. 


Fig.  491.— hand-operated  terminal  valve. 


44 


690 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


closed.     The  air  pressure  running  freely  into  the   tube  forces 
the  carrier  immediately  through  the  tube. 

In  Fig.  492  is  represented  an  automatic  terminal  of  a  store 
or  office  pneumatic  despatch  or  cash-carrier  tube  with  a  catch 
basket.  The  cover  is  thrown  open  which  closes  the  air-press- 
tire   inlet  of  the  supply  pipe  and  is  ready  for  the  ejection  of 


Fig.  492.— automatic  tehmin.\l. 
With  catch  basket. 


Fig.  493.— floor  siation. 


the  tube  messenger  or  carrier.  The  small  cylinder  at  the  right 
contains  a  piston  with  a  projecting  rod  that  unlocks  the  cover 
catch  by  the  air  pressure  when  the  carrier  passes  cross-connec- 
tion and  is  approaching  the  valve. 

In  Fig.  493  is  shown  a  floor-stand  which  is  also  the  air-press- 
ure pipe,  with  the  carrier  pipe  dropping  from  the  ceiling  and 
discharging  into  a  basket.  It  has  an  electric  automatic  opening 
device  and  lock  attached. 


THE    PNEUMATIC    SYSTEM    OF   TUBE    TRANSMISSION, 


691 


S      C3 

s    p. 

^  s 


-    a 

2;     f 


Chapter  XXXI. 


COMPRESSED  AIR  IN 
WARFARE 


693 


COMPRESSED    AIR    IN    WARFARE. 

THE    PNEUMATIC    DYNAMITE    GUN. 

After  many  years  of  experiment  in  the  fruitless  endeavor 
to  throw  a  dynamite  torpedo  from  a  gun  with  powder  or  other 
explosive,  Mr.  D.  M.  Mefford,  of  Ohio,  seems  to  have  been  the 
first  to  indicate  the  correct  solution  of  the  problem,  by  applying 
compressed  air  as  the  propelling  force  in  his  pneumatic  d^^na- 
mite  gun.  The  first  gun,  which  was  of  2-inch  bore  by  28  feet 
in  length,  was  tested  by  Lieut.  E.  L.  Zalinski  in  New  York 
harbor  in  1884,  using  an  air  pressure  of  500  pounds.  A  range 
of  one  and  one-quarter  miles  was  obtained  with  an  accuracy  and 
precision  surprising  when  the  crude  method  of  construction  and 
the  handling  of  the  air  valve  is  considered,  which  latter  was 
largely  due  to  the  personal  equation  of  the  gunner  for  different 
discharges. 

Encouraged  by  the  success  of  these  experiments,  a  4-inch 
gun  was  built,  in  which  air  pressure  at  1,000  pounds  per  square 
inch  was  used,  and  in  which  an  improved  form  of  air  valve  was 
made  automatic  in  action  and  capable  of  delivering  uniform 
amounts  of  air.  In  experiments  with  this  gun  the  practicabil- 
ity of  throwing  dynamite  cartridges  with  an  air  pressure  of 
1,500  pounds  per  square  inch  was  settled  beyond  dispute. 

During  these  experiments  Lieutenant  Zalinski  developed 
the  electric  fuse,  which  largely  contributed  to  the  efficiency  of 
the  gun.  An  8-inch  gun,  60  feet  in  length,  capable  of  throw- 
ing a  shell  containing  100  pounds  of  explosive  to  a  distance  of 
two  miles  with  an  air  pressure  of  1,000  pounds,  was  then  built 
and  mounted  at  Fort  Lafayette  in  1885  ;  which  we  illustrate  in 
Fig,  495,  giving  a  general  view  and  details. 

To  secure  rigidity  of  barrel  it  is  mounted  on  a  truss,  the 


696 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


COMPRESSED    AIR    IN   WARFARE.  697 

whole  turned  upon  the  breech  trunnions  in  the  act  of  elevating 
by  means  of  a  ram  acting  against  the  heel  plate  of  the  truss. 
The  trunnions  rest  in  two  hollow  upright  castings  supported 
upon  the  chassis.  The  castings  also  act  as  air  connections  be- 
tween the  eight  12-inch  by  22-feet  tubes  forming  the  firing  res- 
ervoir, said  tubes  being  secured  on  chassis  and  turning  with  it. 
The  chassis  is  a  front  pintle  arrangement  similar  to  those  in  use 
for  heavy  powder  guns. 

Upon  the  chassis  are  also  mounted  the  cylinders  for  giving 
side  train. 

The  air  supply  from  the  magazine  reservoir  into  which  the 
compressors  deliver,  is  carried  through  the  pintle  around  which 
the  gun  trains,  into  the  firing  reservoir  mounted  on  the  chassis. 

The  firing  valve,  placed  in  the  head  of  one  of  the  trunnion 
supports,  is  capable  of  adjustment,  to  cut  off  the  air  at  any 
desired  point  in  the  barrel  for  varying  ranges.  It  should  be 
borne  in  mind  that  at  each  discharge  only  a  small  per  cent  of 
the  air  in  the  firing  reservoir  is  used,  and  if  desired  the  orig- 
inal pressure  of  1,000  pounds  can  be  immediately  restored  while 
loading  for  the  next  shot,  by  opening  the  connection  between 
the  firing  and  the  magazine  reservoirs,  the  latter  always  being 
maintained  at  a  higher  pressure.  By  this  method  the  firing 
can  take  place  as  rapidly  as  the  shell  can  be  loaded  and  the  gun 
aimed ;  the  best  record  for  speed  being  the  discharge  of  five 
projectiles  in  nine  minutes  and  forty  seconds. 

The  system  is  also  capable  of  greater  accuracy  (within  the 
limits  of  its  range)  than  powder  guns ;  the  initial  pressure  in 
powder  guns  varying  with  the  condition  and  age  of  the  powder 
and  temperature  of  gun  at  instant  of  firing;  whereas,  in  the 
pneumatic  gun,  with  a  known  initial  pressure  and  point  of  cut- 
off, the  resulting  range  must  necessarily  be  constant  for  any 
given  weight  of  projectile  and  degree  of  elevation. 

The  fact  that  the  gUnner  has  under  his  immediate  personal 
control  all  movements  necessary  to  bring  the  gun  to  bear  on 
the  enemy  without  removing  his  eye  from  the  sight  increases 


698  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

the  speed  with  which  accurate  shots  can  be  delivered.  The 
8-inch  gun  was  worked  constantly,  for  experiment  and  exhibi- 
tion, at  1,000  pounds  pressure  for  sixteen  months,  delivering  in 
that  time  a  greater  number  of  shots  than  it  would  be  possible 
to  fire  from  a  powder  gun  without  either  destroying  or  render- 
ing it  unserviceable. 

At  an  elevation  of  35°,  shells  containing  60  pounds  of  explo- 
sives have  been  repeatedl}^  fired  2-}  miles ;  and  at  an  elevation 
of  ^T,°,  shells  containing  100-pound  charges  have  attained  a 
range  of  3,000  5^ards. 

In  the  lower  left-hand  corner  of  the  cut  (Fig.  495)  is  shown 
the  section  of  the  detonator  at  the  point  of  the  shell.  The  fuse 
B  contains  an  electric  battery  in  the  small  case  O,  composed  of 
chemicals  in  a  dry  state.  The  battery  has  a  penetrating  point, 
P,  which  when  driven  in  contact  with  the  insulated  plunger  M 
iV,  to  which  the  circuit  wire  O  is  connected  and  the  circuit  com- 
pleted through  the  circuit-breaker,  fires  the  cap  at  6^  in  the  rear 
of  the  charge.  There  is  much  detail  in  the  arrangement  not 
necessary  to  explain  here,  by  which  the  shell  is  exploded  on  a 
time  circuit  or  by  impact  upon  the  hull  of  a  vessel. 

In  Fig.  496  is  illustrated  the  pneumatic  gun  invented  by 
Lieut.  J.  W.  Graydon,  U.  S.  N.  It  differs  from  the  Zalinski 
gun  in  being  very  much  shorter  and  designed  to  be  operated 
under  a  pressure  of  3,000  pounds  per  sqi.are  inch.  In  a  field- 
piece  as  shown  in  the  cut  the  high-pressure  air  bottles  or  cylin- 
ders are  fixtures  of  the  gun  and  carriage,  and  have  air  capacity 
for  the  discharge  of  a  number  of  shots. 

The  capacity  of  the  bore  of  a  3-inch  field-piece,  10  feet  in 
length,  would  be  something  less  than  a  half  cubic  foot,  includ- 
ing the  projectile,  and  would  require  less  than  a  fourth  cubic 
foot  of  compressed  air  for  discharging  a  projectile  at  1,500 
pounds  air  pressure.  A  battery  of  six  bottles  4  inches  in  diam- 
eter and  5  feet  in  length  would  contain  enough  air  at  3,000 
pounds  pressure  for  twelve  shots. 

Another  form  of  pneumatic  gun  was  brought  out  by  Mr.  Dana 


COMPRESSED    AIR    IN    WARFARE. 


699 


Dudley,  the  "Powder  Pneumatic  Gun,"  in  which  the  air  was 
compressed  at  the  moment  of  firing  by  a  powder  charge ;  thus 
dispensing  entirely  with  the  ponderous  air-compressing  machin- 
ery and  better  adapting  the  gun  to  field  service  for  firing  tor- 
pedoes. It  consists  of  a  gun  barrel  of  light  weight  connected 
at  the  breech  with  a  tube  of  similar  bore  reaching  forward  and 
connecting  with  a  stronger  tube  all  lying  parallel  with  and  be- 
neath the  gun.  A  torpedo  is  placed  in  the  breech  of  the  gun 
just  beyond  the  air  inlet,  and  a  powder  charge  in  the  explosion 
tube  just  beneath  the  gun  breech.  On  firing  the  powder  charge 
the  air  is  compressed  in  the  forward  part  of  the  firing  chamber 


Fig.  496.— the  graydon  pneumatic  gun. 


and  in  the  connecting  tube,  generating  a  pressure  of  from  800  to 
1,000  pounds  per  square  inch.  The  force  of  the  explosion,  cush- 
ioned by  the  two  columns  of  air  intervening  between  the  powder 
and  the  projectile  in  the  central  tube,  acts  upon  the  projectile. 
With  a  slight  noise  and  without  a  particle  of  smoke  or  flame 
the  projectile  is  driven  out  of  the  barrel  and  passes  smoothly 
through  its  trajectory.  About  the  same  effect  is  attained  as 
with  the  regular  pneumatic  gun.  The  extensive  air-compress- 
ing plant  of  the  latter  is,  in  the  case  of  the  Dudley  gun,  repre- 
sented by  a  simple  blank  cartridge. 

Compressed  air  is  now  used  for  controlling  the  recoil  of 
guns  and  mortars,  and  in  the  operation  of  loading,  elevating, 
and  traversing  mortars  and  guns  in  fortifications  it  has  been 
proved  effective  and  a  most  convenient  and  labor-saving  ele- 
ment in  the  operating  of  engines  of  war. 


700  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


COMPRESSED-AIR     SYSTEM      ON     THE     UNITED     STATES     MONITOR 

"TERROR." 

The  use  of  compressed  air  as  a  motive  power  on  board  a 
warship  presents  several  advantages  over  steam  or  hydraulic 
power,  which  renders  it  a  powerful  competitor.  As  compared 
with  steam,  it  is  less  dangerous,  especially  during  an  action, 
when  a  broken  steam-pipe  might  prove  terribly  fatal,  and  it 
enables  certain  parts  of  the  ship  to  be  kept  at  an  even  tempera- 
ture which  would  otherwise  be  rendered  uncomfortably  hot  by 
the  presence  of  steam-piping.  Steam  and  hydraulic  engines, 
moreover,  require  exhaust  pipes  discharging  outside  the  hull  of 
the  ship;  whereas  the  exhaust  from  the  pneumatic  cvlinders 
may  be  turned  into  the  ship  or  into  the  outside  air,  as  may  be 
most  convenient.  There  are  certain  localities  in  a  ship  where 
the  exhaust  from  a  pneumatic  engine  would  prove  a  valuable 
source  of  ventilation,  as,  for  instance,  in  a  turret  crowded  with 
men  and  machinery,  or  in  the  close  confinement  of  a  steering 
room  situated  below  the  protective  deck.  As  compared  with 
h3'draulic  power,  the  compressed-air  system  is  cleaner  and 
more  convenient,  and  free  from  the  discomfort  that  arises  from 
the  leaking  of  hydraulic  pipes  and  cylinders. 

In  1 890  the  Navy  Department  authorized  a  complete  pneu- 
matic system  for  steering  the  monitor  Terror  and  operating  her 
turrets.  Owing  to  delays  in  the  completion  of  the  ship,  the 
new  system  was  not  tried  until  late  in  1896,  when  the  whole  of 
the  elaborate  plant  was  put  to  a  thorough  test  at  sea,  and  gave 
the  greatest  satisfaction  to  the  naval  experts.  As  the  Terror 
was  the  first  vessel  in  the  world  to  be  so  equipped,  there  was 
considerable  anxiety  as  to  the  success  of  the  experiment ;  but 
now  that  the  plant  has  demonstrated  its  ability  to  do  all  that 
was  claimed,  its  success  has  stimulated  the  use  of  compressed 
air  in  similar  lines  in  the  navies  of  Europe. 

Directly  below  the  centre  of  the  turret  is  a  pneumatic  load- 


COMPRESSED    AIR    IN    WARFARE. 


701 


ing  machine,  which  rotates  upon  a  vertical  shaft,  and  may  be 
swung  to  the  right  or  left  as  desired.  The  500-pound  shell 
and  the  cartridge,  the  latter  in  two  parts,  are  run  out  from  their 
respective  rooms  on  a  overhead  trolley  and  placed  in  the  tray 
of  the  loading  machine,  as  shown  in  Fig.  497.  The  tray  is 
pivotally  attached  to  the  body  of  the  machine  by  a  set  of  par- 


Fig.  497.  — ammunition  elevator  and  pneumatic  lift  for  loading  the  elevator. 

allel  rods  and  a  lever  which  carries  at  its  inner  end  a  circular 
rack.  Above  the  rack  is  an  air  cylinder  whose  piston  rod  ter- 
minates in  a  vertical  rack  which  engages  the  circular  rack.  By 
admitting  air  at  the  top  of  the  cylinder,  the  tray  with  its  load 
is  raised  to  the  required  height  and  the  latter  is  placed  in  the 
pockets  of  the  loading  car. 

There  are  two  of  these  cars,  one  for  each  gun,  and  they 


702  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

travel  upon  two  vertical  hoists  or  trackways  which  lead  up  to 
the  breech  of  the  guns.  The  hoisting  is  done  by  two  pneu- 
matic cylinders  located  on  the  floor  of  the  turret  between  the 
guns.  Attached  to  each  piston  rod  and  beneath  each  cylinder 
is  a  set  of  multiplying  sheaves.  Over  these  passes  a  wire  rope, 
one  end  of  which  is  fastened  to  the  floor  of  the  turret,  the  other 
end  being  carried  to  the  loading  car.  The  speed  of  the  rope 
is  so  adjusted  that  the  full  stroke  of  the  pistons  will  serve  to 
hoist  the  loading  car  from  the  floor  of  the  handling  room  to 
the  breech  of  the  gun. 

By  reference  to  Fig.  497,  it  will  be  seen  that  the  loading 
car  contains  three  parallel  pockets,  which  rotate  within  the 
frame  of  the  car,  friction  wheels  being  interposed  to  facilitate 
the  movement.  One  of  the  pockets  carries  the  shell  and  the 
other  two  the  powder  charge.  The  car  is  automatically  brought 
to  a  stop  with  the  lowest  pocket  containing  the  shell  imme- 
diately in  line  with  the  breech  of  the  gun. 

It  is  then  pushed  home  by  a  telescopic  rammer  which  is 
operated  by  compressed  air,  the  valve  which  admits  the  air 
being  worked  by  a  man  who  sits  astride  of  the  cylinder  (Fig. 
498).  It  will  be  noticed  that  the  rammer  is  carried  by  a  bracket 
bolted  to  an  extension  of  the  gun  carriage,  and  it  is  conse- 
quently held  at  all  times  in  true  line  wath  the  bore  of  the  gun. 
After  the  shell  has  been  rammed  home,  the  loading  car  is  rotated 
and  the  two  sections  of  the  powder  cartridge  are  brought  suc- 
cessively opposite  the  breech  and  pushed  home.  The  breech 
plug  is  then  swung  round,  thrust  into  place,  and  locked. 

The  air  for  driving  the  various  pneumatic  devices  is  com- 
pressed by  two  separate  engines,  one  being  placed  in  the  hold 
near  the  forward  turret  and  the  other  near  the  after  turret  on 
the  berth  deck.  The  working  pressure  is  125  pounds  per 
square  inch,  and  there  is  no  reservoir  for  the  air  except  an 
8-inch  pipe,  which  runs  through  the  vessel  and  supplies  the  two 
turrets  and  also  the  steering  device  in  the  steering-room  at  the 
extreme  after  end  of  the  ship.     These  two  engines  supply  suffl- 


COMPRESSED    AIR    IN    WARFARE. 


703 


cient  air  for  turning  the  turrets,  elevating  the  guns,  lifting  the 
ammunition  into  the  cages,  raising  the  cages  to  the  breech  of 
the  gun,  ramming  home  the  charge,  closing  the  breech,  check- 
ing the  recoil,  and,  lastly,  and  most  important  operation  of  all, 
steering  the  ship  itself. 

The  two  turning  engines  are  placed  upon  the  floor  of  the 
turret,  one  on  each  side  of  the  big  guns.     Each  engine  has  two 


Fig.  498.— chakging  the  gu:-;  ;   the  loading  cak  is  between  the  telescopic  hammer 
and  the  bueech  of  the  gun. 


cylinders,  8  inches  in  diameter  by  14  inches  stroke.  A  worm  on 
the  crank  shaft  operates  a  set  of  gears  by  which  the  power  is 
multiplied  many  times  over  before  it  reaches  a  driving  pinion, 
which,  in  common  with  the  engine  and  gears,  is  firmly  bolted 
to  the  framing  of  the  turret  and  turns  with  it.  The  pinion 
meshes  with  a  large  circular  rack  which  is  bolted  to  the  deck  of 
the  ship  and  lies  immediately  within  the  circular  steel  track 
upon  which  the  turret  rotates.  The  engines  are  controlled  by 
suitable  levers  and  hand -wheels  situated  within  easy  reach  of 


704 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


COMPRESSED    AIR    IX    WARFARE,  705 

the  officer  in  the  sighting  hood,  the  latter  being  placed  over 
and  between  the  guns. 

The  elevation  and  depression  of  the  gun  are  effected  by 
means  of  a  massive  ram,  which  is  hinged  to  the  floor  of  the 
turret  and  bears  against  a  shoe  on  the  under-side  of  the  gun 
carriage  near  the  breech  of  the  gun.  On  each  side  of  the  turret 
is  a  cylinder  containing  glycerin  and  water,  a  portion  of  which, 
when  the  gun  is  to  be  elevated,  is  forced  by  compressed  air  into 
the  ram,  the  supply  being  regulated  by  valves  which  are  oper- 
ated by  means  of  levers  in  the  sighting  station.  With  his  eye 
at  the  telescope  and  his  hand  upon  the  levers  which  control  the 
air  valves  of  the  turning  and  elevating  machinery,  the  officer 
brings  the  cross-hairs  of  the  telescope  to  bear  upon  the  mark, 
and  by  pressing  an  electric  button  hurls  a  500-pound  steel  pro- 
jectile with  unerring  precision  at  the  hostile  ship. 

The  recoil  of  the  gun  is  controlled  by  two  pneumatic  cylin- 
ders, 14  inches  in  diameter  and  40  inches  in  length.  The  cyl- 
inders below  the  breech  are  secured  to  the  gun  carriage  and  the 
pistons  to  the  gun.  Before  firing,  the  pressure  on  the  recoil 
side  of  the  pistons  is  about  500  pounds  per  square  inch.  As 
the  gun  recoils,  carrying  the  pistons  with  it,  this  pressure  is 
rapidly  increased  by  compression.  To  reduce  the  pressure  at 
the  end  of  the  recoil,  a  tapered  rod  is  provided,  which  passes 
through  the  centre  of  the  piston  and  allows  the  air  to  pass  more 
and  more  freely  to  the  counter  side  of  the  piston  as  the  gun 
returns.  The  residual  pressure  is  utilized  to  return  the  gun  to 
its  firing  position.  Perhaps  there  is  no  part  of  the  many  opera- 
tions performed  by  compressed  air  on  the  Terror  in  which  the 
power  shows  to  better  advantage — the  elasticity  of  the  air  pre- 
venting all  shock  and  providing  an  easy  cushion  in  the  recoil 
and  counter  recoil. 

The  last  and  most  important  duty  performed  by  the  com- 
pressed air  is  that  of  steering  the  ship.  The  work  is  performed 
by  two  long  horizontal  cylinders  which  are  arranged  one  on 
each  side  of  the  tiller.  They  are  provided  with  a  common 
45 


706  CCMPRESSEl)    AIR    AND    ITS    APPLICATIONS. 

piston  rod,  in  the  centre  of  ^vhich  is  a  hollow  crosshead  in 
which  the  tiller  is  free  to  slide  as  it  is  swung  right  or  left  by 
the  movement  of  the  pistons.  Compressed  air  is  admitted  to 
the  outer  ends  of  the  cylinders  by  means  of  a  D  valve,  the  air 
being  simultaneously  admitted  at  the  back  of  one  piston  and 
exhausted  from  the  other,  according  as  the  helm  is  to  be  put 
over  to  port  or  to  starboard.  Air  is  also  admitted  at  all  times 
at  the  inner  ends  of  the  cylinders,  and  a  pipe  connects  them, 


Fig.  500.— pneumatic  steering  apparatus  on  the  monitor  "terror." 

so  that,  as  the  pistons  move,  the  air  may  flow  freely  from  the 
inner  end  of  one  cylinder  to  the  inner  end  of  the  other.  In  the 
centre  of  the  connecting  pipe  is  a  by-pass  valve,  which  is  open 
when  the  tiller  is  being  moved,  but  closes  when  it  has  been 
traversed  the  desired  angle,  and  holds  the  air  imprisoned  in 
the  cylinders,  thus  locking  the  tiller  between  two  elastic  cush- 
ions. The  heavy  shocks  to  which  the  tiller  is  subject  in  rough 
weather  will  thus  be  received  and  absorbed  by  the  air,  and  the 
framing  of  the  ship  will  be  proportionately  relieved  of  the 
strain. 

The  general  use  of  compressed  air  on  shipboard  may  not  in 
many  cases  be  as  economical  as  steam,  but  considering  for  all 


COMPRESSED    AIR    IN    WARFARE.  707 

emergency  cases  and  where  a  constant  pressure  is  required  at 
points  distant  from  the  boilers,  there  is  nothing  equal  to  com- 
pressed air  for  operating  auxiliary  fire,  bilge,  and  water  service 
pumps;  steering  engine;  anchor  engine  ;  boat  cranes  ;  winches; 
turret-turning  engines;  hydraulic  cylinders  for  working  guns; 
ammunition  hoists;  ash  hydropneumatic  hoists;  feed  pumps; 
smoke  hose  for  guns;  whistle  and  siren;  to  send  messages;  to 
clear  a  compartment  of  water  when  flooded;  to  ventilate  and 
to  heat  and  cool  the  ship. 

Compressed  air  is  better  than  steam  for  auxiliary  use  on 
board  ship,  for  the  following  reasons: 

The  ship  is  cooler  in  summer,  and  men  are  not  debilitated 
by  the  heat;  there  are  no  hot  bulkheads  all  over  the  ship;  the 
auxiliary  machinery  and  pipes  last  much  longer;  half  the  num- 
ber of  valves,  pipes,  etc.,  are  needed;  there  are  no  ventilating 
blowers  needed  to  neutralize  the  heater  lines  doing  the  work; 
there  is  great  saving  in  cost  of  plants  and  in  the  cost  of  oil ; 
no  pipe  coverings  are  needed;  the  machines  are  ready  for  use 
at  once ;  there  are  fewer  men  on  watch  in  port,  and  more  for 
general  work. 


Chapter  XXXII. 


COMPRESSED  AIR  WORK 


COMPRESSED    AIR    WORK. 

COMPRESSED    AIR    FOR    RAISING    WATER, 

The  air-lift  pump  is  said  to  have  been  invented  in  the  eigh- 
teenth century  and  in  use  at  Freiberg,  Saxony.  Siemens  in 
England  experimented  with  the  air  lift  in  the  middle  of  the 
nineteenth  century,  and  it  was  patented  as  an  air  ejector  by 
McKnight  in  1864.  The  principle  of  its  action  became  a  theme 
with  Dr.  J.  G.  Pohle,  and  to  whom  two  patents  were  issued, 
Nos.  338,295  and  347,196,  covering  the  system  of  elevating 
water  by  admixture  of  air  under  compression  suitable  for  the 
height  that  the  water  was  to  be  raised.  This  system,  however, 
required  a  depth  of  water  in  the  well  more  than  equal  to  a 
height  to  which  the  water  was  to  be  lifted. 

The  original  Pohle  system  has  been  modified  and  improved 
with  a  number  of  patents  on  special  points  in  the  system  with 
small  gains  in  efficiency.  Dr.  Pohle  also  introduced  compound- 
ing or  stage-lifting,  which  has  been  made  available  to  such  an 
extent  that  it  is  now  possible  to  lift  water  to  great  heights  from 
an  ordinary  sump  in  a  mine  or  from  ordinar}^  wells. 

We  illustrate  in  Fig.  501  the  compressor,  receiver,  air  and 
lift  pipe  as  usually  operated  in  deep  wells,  in  which  the  press- 
ure in  the  air  pipe  must  be  greater  than  the  hydrostatic  press- 
ure of  the  water  at  the  bottom  of  the  pipe,  and  in  quantities 
sufficient  to  make  the  ascending  column  of  air  and  water  in  the 
flow  pipe  lighter  in  its  total  height  than  the  weight  of  an  equal 
column  of  solid  water  of  the  depth  of  the  well  from  the  surface 
of  the  water  to  the  bottom  of  the  pipe,  thus  making  this  prin- 
ciple in  pumping  water  essentially  a  differential  gravity  system. 

The  air-lift  pump  proper  consists  of  only  two  plain  open- 
ended  pipes,  the  larger  one  with  an  enlarged  end  piece  consti- 


712 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


tuting  the  discharge  pipe,  and  the  smaller  one  let  into  the  en- 
larged end  piece  of  the  discharge  pipe  constitutes  the  air  inlet 
pipe,  through  which  the  compressed  air  is  conveyed  to  the 
enlarged  end  piece  to  the  under  side  of  the  water  to  be  raised. 
No  valves,  buckets,  plungers,  rods,  or  other  moving  parts  are 

used     within     the 
pipes  or  well. 

I  n  pumping, 
compressed  air  is 
forced  through  the 
air  pipe  into  the 
enlarged  end  at  the  bottom  of  the  water  pipe; 
thence  by  the  inherent  expansive  force  of  the 
compressed  air.  layers  or  bubbles  of  air  are 
formed  in  the  water  pipe,  which  lift  and  dis- 
charge the  water  layers  through  the  upper  end 
of  the  water  discharge  pipe.  At  the  beginning 
of  the  operation  the  water  surface  outside  of  the 
pipe  and  the  water  surface  inside  of  the  pipe  are 
at  the  same  level ;  hence  the  vertical  pressures 
per  square  inch  are  equal  at  the  submerged  end 
of  the  pipe,  outside  and  inside.  As  air  is  forced 
into  the  lower  end  of  the  water  pipe,  it  forms  alternate  layers 
with  the  water,  so  that  the  pressure  per  square  inch  of  the 
column  thus  made  up  of  air  and  water,  as  it  rises  inside  of  the 
water  pipe,  is  less  than  the  pressure  of  water  per  square  inch 
outside  of  the  pipe. 

Owing  to  this  difference  of  pressure,  the  water  flows  contin- 
ually from  the  outside  to  within  the  water  pipe  by  gravity 
force,  and  its  ascent  through  the  pipe  is  free  from  shock,  jar, 
or  noise  of  any  kind. 

These  air  sections  or  strata  of  compressed  air  form  closed 
bodies,  which,  in  their  ascent  in  the  act  of  pumping,  permit 
no  slipping  or  back  flow  of  water.  As  each  air  stratum  pro- 
gresses upward  to  the  spout,  it  expands  on  its  way  in  proportion 


Fig.      501.— air 
lift  pump. 


COMPRESSED    AIR    WORK. 


7^1 


as  the  overlying  weight  of  water  is  diminished  by  its  discharge, 
so  that  the  air  section,  which  may  have  been  say  50  pounds  per 
square  inch  at  first,  will  be  only  1.74  pounds  when  it  underlies 
a  water  layer  of  four  feet  in  length  at  the  spout;  until  finally 
this  air  section,  when  it  lifts  up  and  throws  out  this  four  feet 
of  water,  is  of  the  same  tension  as  the  normal  atmosphere ; 
thus  proving  that  the  whole  of  its  energy  was  used  in  work, 
and  that  this  pump  is  a  perfect  expansion  engine. 

As  the  weight  of  the  water  outside  of  the  discharge  pipe 
(the  head)  is  greater  per  square  inch  than  the  aggregate  water 


n:  ^  V' 

Fig.    502.— THF   CLAYTON    DUPLEX   AIR   COiMPRESSOK   AND  AIR  LIFT   I'LMI'LNf.   APPARATUS. 


sections  within  the  pipe  when  in  operation,  it  follows  that  the 
energy  due  to  this  greater  weight  is  utilized  in  overcoming  the 
resistance  of  entry  into  the  pipe,  and  all  the  friction  within  it. 

The  Pohle  "air-lift"  pump  has  been  found  to  give  above 
80  per  cent  of  efficiency  from  the  air  receiver  in  water  pipes 
of  large  diameter,  and,  as  a  rule,  above  70  per  cent  in  small- 
sized  pipes.  It  retains  this  efficiency  without  repairs,  or  until 
the  pipes  rust  through,  whereas  ordinary  bucket-and-plunger 
pumps  gradually  lose  efficiency  from  the  first  stroke  they  make, 
and  lose  it  rapidly  if  the  water  contains  sand  or  is  acid  in  char- 
acter. 


714  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

The  secret  of  the  air-lift  pump  action  is  in  the  high  velocity 
with  which  the  air  and  water  are  discharged  through  the  educ- 
tion pipe.  Withcjut  this  high  velocity  there  would  be  no  piston- 
like sections  except  perhaps  in  a  small  glass  tube  model  where 
capillary  attraction  takes  the  place  of  velocity. 

As  the  pump  has  no  valves,  no  standing  water  remains  in 
the  pump  column  after  the  operation  of  pumping;  it  recedes 
into  the  well,  and  there  is  none  left  to  freeze  in  cold  weather. 
The  capacity  of  the  pump  is  unlimited,  and,  with  the  proper 
proportions  of  air  to  the  water,  will  work  efficiently  in  pipes 
several  feet  in  diameter.  Estimates  have  been  made  which 
indicate  that  a  30-inch  pipe  will  deliver  16,660  gallons  per  min- 
ute, equal  to  1,000,000  gallons  per  hour. 

As  sand,  silt,  gravel,  and  bowlders  in  water  form  no  obsta- 
cles to  interfere  with  the  action  of  the  pump,  its  adaptability 
for  dredging  is  suggested  as  well  as  its  utility  for  pumping 
sewage.  Experience  has  proved  that,  by  the  use  of  this  con- 
stant upward  flow  of  water,  artesian  wells  have  been  freed  from 
their  accumulated  sedimentary  deposits,  as  well  as  that  lodged 
in  the  fissures  and  crevices  of  their  wall  rock,  and  have  been 
thus  made  to  yield  greater  quantities  of  water  than  they  ever 
did  before.  For  chemical  uses,  and  for  the  liquids  of  the  arts, 
there  is  no  superior  method  than  the  "air  lift."  It  is  used  suc- 
cessfully for  raising  sulphuric  acid  of  high  specific  gravities, 
and  is  well  adapted  for  ore-leaching  works,  vinegar  works, 
sugar  refineries,  dye  works,  paper-pulp  works,  etc. 

As  an  irrigating  pump  for  raising  subterranean  water  in  the 
arid  regions  of  the  West,  its  field  of  usefulness  is  very  promis- 
ing, for  with  one  air-compressing  plant  at  a  central  station,  a 
number  of  wells,  widely  separated  from  one  another,  may  be 
simultaneously  pumped  by  branches  of  air-conveying  pipes, 
taken  from  a  main  air  pipe  from  the  air  compressor;  for  com- 
pressed air  may  be  conveyed  for  miles  without  material  loss  of 
power. 

It  often  happens  that  a  single  well  does  not  yield  the  quan- 


COMPRESSED   AIR    WORK.  715 

tity  of  water  desired,  but  that  a  number  of  wells  would  give  the 
satisfactory  result.  By  the  old-fashioned  deep-well  pump,  each 
well  would  require  a  separate  "steam  head,"  separate  sets  of 
rods,  and  the  other  paraphernalia,  which,  with  the  condensa- 
tion of  the  steam,  when  conveyed  to  the  several  steam  heads, 
would  be  very  costly  in  the  first  outlay,  and  very  wasteful  of 
power  in  its  maintenance,  to  say  nothing  of  loss  of  time  in  re- 
pairs. By  the  Pohle  process,  but  one  air-compressing  plant  is 
required,  and  this  may  be  placed  in  the  engine  room  or  the 
boiler  house,  directly  under  the  eyes  of  the  engineer,  from 
whence  the  air  may  be  conveyed  to  the  several  wells,  all  of 
which  may  be  pumped  simultaneously  and  economically. 

In  Fig.  501  is  illustrated  the  air-lift  system  of  the  Ingersoll- 
Sergeant  Drill  Company,  New  York  City,  with  which  company 
Dr.  Pohle  was  associated  in  the  last  years  of  his  life. 

In  the  early  trials  for  efficiency  of  the  air  lift  some  curious 
comparisons  were  brought  out  relative  to  the  ratio  of  the  lift  to 
the  depth  of  submersion  and  the  relative  air  pressure  due  to 
submersion. 

Thus  with  16  pounds  air  pressure  with  41  feet  water  lift  and 
10  feet  submergence,  68  cubic  feet  of  free  air  per  minute  lifted 
-|  cubic  foot  of  water  41  feet  high,  giving  a  computed  efficiency 
of  3^  per  cent  of  the  steam  power.  The  efficiency  was  found 
to  decrease  with  the  increase  of  air  pressure  above  what  was 
necessary  to  do  the  work;  for  instance,  with  an  equal  sub- 
mergence and  lift  of  26  feet  and  an  air  pressure  of  20  pounds, 
64  cubic  feet  of  free  air  pumpeJ  14  cubic  feet  of  water  26  feet 
high  per  minute,  showing  an  efficiency  of  19  per  cent  of  the 
steam  power  in  the  compressor.  When  the  air  pressure  was 
reduced  to  12-1-  pounds,  using  26  cubic  feet  of  free  air  per  min- 
ute and  pumping  Si  cubic  feet  of  water  26  feet  high  per  minute, 
the  efficiency  was  raised  to  42  per  cent.  It  was  found  on  trials 
that  on  a  deeper  submergence  of  i  to  1.6  the  efficiency  rose  to 
53  per  cent,  and  in  all  trials  was  greatest  at  the  lowest  pressure 
that  the  lift  could  be  operated.      It  was  found  on  a  general  aver- 


yl6  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

age  that  the  efficiencies  that  may  be  expected  from  the  best 
conditions  for  air  compression  may  be  stated  as  follows : 
Height 


Submergence 


=     .5   efficiency   50  per  cent. 


I.O 

40 

1-5 

30 

2.0 

25 

Mathematicians  have  formulated  some  complicated  equations 
in  relation  to  the  action  of  the  air  in  the  ascending  column  of 
water ;  but  as  the  air  bubbles  vary  in  size  according  to  the  form 
of  the  injecting  nozzle,  and  as  their  coalescence  and  expansion 
produce  so  many  variable  factors,  reliable  results  can  be  ob- 
tained only  from  actual  tests,  and  even  these  are  merely  ap- 
proximate. 

In  a  test  of  the  Pohle  air-lift  made  at  De  Kalb,  111.,  the  air 
pipe  was  placed  inside  of  the  well  pipe  with  a  water  lift  of  133 
feet,  and  the  submerged  nozzle  123  feet  below  the  surface,  a 
nearly  equal  ratio.  The  well  pipe  was  6  inches  diameter,  air 
pipe  2^-  inches,  thus  adding  about  50  per  cent  to  the  friction  of 
the  ascending  water  and  giving  to  the  whole  length  of  256  feet 
an  irregular  annular  space  for  the  passage  of  the  water  and  air. 
With  the  expenditure  of  42.7  horse-power  indicated,  there  was 
raised  207  gallons  of  water  133  feet,  with  a  volume  of  310  cubic 
feet  of  free  air  per  minute.  The  efficiency  was  found  to  be 
17I-  per  cent.  This  shows  very  plainly  that  the  friction  of  an 
internal  air  pipe  causes  a  loss  of  efficiency. 

A  series  of  trials  with  a  gang-well  system  on  the  Pohle  plan 
was  made  at  Rockville,  111.  In  casings  of  6\  inches  diameter 
inserted  in  four  wells,  260  feet  below  the  overflow,  and  air 
pipes  i^  inches  diameter,  let  down  250  feet,  all  in  8-inch  drilled 
wells.  After  several  trials  with  return  bends  and  small  nozzles 
at  the  bottom  of  the  air  pipes  with  unsatisfactory  results  as  to 
water  flow,  the  bottom  of  the  air  pipe  was  closed  and  the  sides 
slotted  for  20  inches  up  from  the  bottom,  giving  a  full  and  free 
opening  for  the  air  without  any  obstruction  to  the  upflow  of  the 


COMPRESSED    AIR    WORK. 


717 


water.  In  this  manner  the  service  was  raised  from  1,000  gal- 
lons to  1,400  gallons  per  minute,  but  still  showing  an  efficiency 
of  only  24  per  cent. 

Much  doubt  has  existed  from  the  early  years  of  the  air-lift 
system  as  to  the  possibilities  in  regard  to  conveying  the  water 
to  a  distance  or  direct  to  an  elevation  at  a  distance  from  the 
well.  Lately  there  has  been  constructed  at  Point  Pleasant,  W. 
Va.,  on  the  bank  of  the  Ohio  River,  a  water-works  employing 
the  air-lift  system  to  obtain  water  filtered  into  the  gravelly  soil 
beneath  the   river.     The   compressor  was  located  in  a  power 


OhiJjiUer  RailiwtJ 


Fig.  503.— profile  of  the  point  ple.asant  water-works. 


house  500  feet  distant  from  the  location  of  the  wells  on  the  river 
bank.  The  receiving  basin  is  situated  at  the  top  of  the  river 
bank,  67  feet  above  the  top  of  the  well  pipes  and  400  feet  from 
the  low-water  bank  of  the  river.  In  Fig.  503  is  shown  a  profile 
of  the  situation.  Well  casings  10  inches  in  diameter  were 
driven  to  the  rock  about  40  feet  in  depth. 

After  the  lo-inch  casings  were  in  place  lo-inch  holes  were 
drilled  in  the  underlying  rock  1 16  feet  deep,  and  cased  8  inches 
inside  diameter  from  bottom  to  top.  This  casing  was  also  per- 
forated similarly  to  the  outer  one,  only  the  holes  were  larger — 
-^  inch.  The  space  between  the  two  casings  was  tightly  calked 
at  the  top  to  prevent  water  entering  the  wells  at  this  point. 


7l8  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

Four-inch  discharge  pipes  and  i-]-inch  air  pipes  were  properly 
fitted  and  suspended  in  each  of  the  wells,  with  their  extremities 
I  lo  feet  below  the  top  of  the  8-inch  casing. 

Both  pipes  were  suspended  from  a  water-tight  cap,  resting 
on  the  top  of  the  8-inch  casing.  It  will  be  observed  that  no 
water  can  enter  these  wells  except  through  the  perforations  in 
the  casings,  which  are  lo  feet  to  20  feet  below  the  flowing 
water  in  the  river.  None  can  enter  at  the  bottom.  It  was  the 
desire  to  allow  the  river  water  to  enter  the  wells  only  through 
the  perforations  after  having  passed  through  the  sand  strata 
mentioned,  which  would  serve  as  a  filter ;  which  has  proved  that, 
however  muddy  the  river  may  be,  the  water  taken  from  the 
wells  is  bright  and  sparkling  at  all  times. 

Just  when  the  wells  were  completed  and  the  pipes  in  place 
and  extending  up  the  sloping  river  bank  a  short  distance,  the 
river  rose  over  the  wells.  For  two  months  the  wells  stood 
unused.  In  the  mean  time  the  reservoir,  receiving  basin,  and 
power  house  were  completed,  and  the  work  advanced  as  fast  as 
possible.  Just  as  soon  as  the  air  compressor  was  in  place  the 
air  pipes  were  connected  up  and  the  wells  tested  before  the 
discharges  were  extended  to  the  receiving  basin.  One  well  was 
found  with  a  deposit  of  sand  in  the  bottom  reaching  5  feet  above 
the  foot  of  the  discharge  pipe.  Several  unsuccessful  efforts 
were  made  to  force  air  into  this  well.  The  river  having  re- 
ceded, the  air  pipe  was  disconnected  at  the  top  of  the  well  and 
a  f-inch  gas  pipe  coupled  and  lowered.  It  stopped  5  feet  from 
the  bottom.  It  was  churned  a  few  minutes  and  soon  went 
down  the  remaining  5  feet.  Again  the  air  pipe  was  coupled 
and  the  air  pressure  increased  to  90  pounds  per  square  inch. 
The  effect  was  almost  startling,  but  gratifying.  The  obstruc- 
tion was  cleared  out  very  quickly.  No  other  system  of  pump- 
ing could  possibly  have  accomplished  the  clearing  out  of  this 
well  of  the  sand  deposit. 

The  discharge  and  air  pipes  to  each  well  are  independent. 
That   is,  each  well   has  a  separate   discharge  to  the  receiving 


COMPRESSED    AIR    WORK.  719 

basin  and  a  separate  air  pipe  from  the  receiver.  These  are 
carefully  graded  and  are  not  exposed  at  any  point  except  where 
the  discharges  pass  through  the  top  of  the  walls  of  the  receiv- 
ing basin,  and  have  open  discharge. 

The  working  pressure  is  from  45  to  50  pounds,  varying  with 
different  river  levels. 

The  discharge  of  water  is  not  constant,  however,  but  irreg- 
ular or  intermittent,  as  though  the  air  and  water  formed  alter- 
nate strata  or  volumes  within  the  discharge  pipes.  It  varies 
with  the  depth  of  water  in  the  river,  ranging  from  i  volume 
of  water  to  8  volumes  of  free  air,  to  i  to  6.  As  the  river  is 
constantly  rising  and  falling  and  is  frequently  25  to  40  feet 
deep  over  the  wells,  the  pressure  on  the  sand  surrounding  the 
wells  is  constantly  changing  and  affects  the  capacity  of  them 
as  well  as  the  necessar}'  air  pressure  to  pump  them. 

The  reservoir  is  situated  about  i^  miles  distant  and  at  225 
feet  elevation.  Water  is  taken  from  the  receiving  basin  by 
belt-driven  triplex  outside-packed  plunger  pumps,  9  inches 
diameter  by  12 -inch  stroke,  operated  at  37  revolutions  per 
minute,  delivering  about  22,000  gallons  per  hour. 

As  there  is  no  demand  in  the  town  for  electric  current  dur- 
ing the  day,  the  works  are  operated  at  night  only.  Usually  the 
air  compressor  is  operated  one  night,  and  the  following  night 
the  forcing  pumps.  The  water  received  the  previous  night  in 
the  settling  or  receiving  basin  has  about  twelve  hours  to  be- 
come cleared  of  any  sand  brought  with  it  from  the  wells  before 
going  to  the  reservoir.  This  basin  has  a  capacit}'  of  about 
225,000  gallons;  the  reservoir  about  three  times  this  quantity. 
The  construction  of  the  receiving  basin  is  the  same  as  the  reser- 
voir. The  engine  has  ample  power  to  operate  all  the  machin- 
ery at  the  same  time.  Two  men  only  are  required  to  attend 
the  combined  plant.  In  addition  to  the  public  and  private 
consumption  of  water,  two  busy  railroads  are  consumers.  All 
customers  are  served  by  meter,  and  therefore  there  is  practi- 
cally no  waste. 


720  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

There  can  be  no  doubt  that  water  taken  by  air  m  this  man- 
ner is  purified  to  some  extent,  the  admixture  of  air  serving  to 
oxidize  and  destrcjy  organic  matter.  Samples  of  the  water 
taken  are  bright  and  sparkling,  have  no  odor,  and  remain  ap- 
parently unchanged.  There  probably  is  not  another  town  of 
5,000  inhabitants  in  the  country  that  has  a  better  or  more  c(jm- 
plete  combined  water  and  light  works.  Certainly  there  is  not 
another  town  of  any  size  on  the  banks  of  the  Ohio  River  from 
Pittsburg  to  Cairo  that  has  better  water,  if  as  good. 

The  works  have  been  in  constant  operation  since  built. 

What  has  been  accomplished  at  Point  Pleasant  can  be  done 
at  hundreds  of  other  small  towns  similarly  situated  where  there 
is  no  water-works.  Here  it  has  been  demonstrated  that  bright, 
sparkling  water  can  be  obtained  from  a  muddy,  filthy  stream 
without  the  use  of  chemicals  or  mechanical  filters. 

Just  use  the  filter  nature  has  so  abundantly  supplied  at  the 
bottom  of  such  streams,  and  by  proper  arrangement  of  the 
pumping  system  combined  with  an  electric-lighting  system, 
thus  economizing  the  operating  expenses  to  a  minimum,  estab- 
lish first-class  water  and  electric  service  on  a  paying  basis  when 
neither  separately  would  pay  operating  expenses. 

The  air-lift  system  is  undoubtedly  the  simplest  as  well  as 
the  best  of  all  known  methods  of  serving  such  towns  with  good 
water.  Nor  is  the  system  less  applicable  to  larger  towns,  as 
well  as  to  factory  and  domestic  supply. 

Artesian  wells,  or  wells  supplied  from  land  sources,  gener- 
ally yield  hard  water  or  water  highly  charged  with  mineral 
salts.  The  water  at  Point  Pleasant  is  soft,  pleasant,  and  whole- 
some. The  railway  companies  using  it  speak  very  highl}-  of 
it.  It  is  simply  Ohio  River  water  freed  of  filth  and  all  objec- 
tionable matter  that  render  it  so  disgusting  at  many  towns 
along  the  stream. 


COMPRESSED    AIR    WORK. 


721 


THE    COMPOUND    AIR    LIFT. 

The  idea  of  compounding  the  air  lift  was  first  proposed  by 
Dr.  Pohle,  and  has  since  come  into  use  for  shallow  sumps.  Fig. 
504  represents  the  conditions  of  a  sump  of  about  one-quarter  of 
the  total  lift  in  depth,  in  which  an  auxil- 
iary pipe  is  introduced  to  receive  the 
water  at  about  twice  the  depth  of  the 
sump  to  act  as  a  pump  well  for  a  higher 
lift.  By  this  method  the  inconvenience 
and  cost  of  a  deep  shaft  or  boring  may  be 
avoided  and  the  compound  system  quickly 
applied  in  emergencies. 

As  yet  we  have  no  data  as  to  its  effi- 
ciency for  permanent  use,  but  there  is  no 
doubt  that  economy  due  to  decreased  air 
pressure  will  be  found  to  warrant  its 
adoption  in  mine  and  drainage  work. 

MULTIPLE    STAGE    AIR-LIFT    PUMPING. 

In  Fig.  505  we  illustrate  the  possibili- 
ties in  the  work  of  compressed  air  in 
pumping  water  to  great  heights  from 
shallow  sumps  by  the  Pohle  air-lift  sys- 
tem. In  order  to  show  the  detail  of  opera- 
tions the  illustration  is  spread  out.  In 
practice  the  several  wells  may  be  bunched  together  to  occupy 
the  smallest  space  in  a  mine  shaft.  It  will  be  readily  perceived 
that  but  one  air  pressure  is  needed,  no  more  than  sufficient  to 
operate  the  highest  lift  in  the  multiple-stage  system.  The  lesser 
lifts  may  be  regulated  by  valves  in  the  air  branches  to  exactly 
meet  the  volume  and  pressure  required  for  the  lower  lifts.  Its 
air  economy  may  balance  the  cost  of  a  deep  sump,  but  its  effi- 
ciency is  yet  to  be  tested. 
46 


Fig.  504.— duplex  air  lift. 


722 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


Fig.  505.— multiple  stage  air  lift. 


THE     AIR-LIFT     PUMPING     SYSTEM     OF    THE 

PNEUMATIC    ENGINEERING    COMPANY, 

NEW    YORK    CITY. 

The  special  feature  of  the  air-lift  pump- 
ing system  of  this  company  is  due  to  the 
patents   of   Mr.  S.  W.   Titus,  which  claim 
an  air  tube  within  the  well  tube,  closed  at 
the   lov/er  end  and   perforated  with  lateral 
orifices   at  different    points   in   its    height 
with   a   series  of  cylindrical  valves  corre- 
sponding with  the  orifices,   differentially, 
and  attached  to  a  central  stem  projecting 
above  the  top  of  the  air  pipe  and  terminat- 
ing in   a  screw,   yoke,   and    valve    wheel. 
The    relative  positions  of  the  orifices  and 
valves  are  so  arranged  that  they   can  be 
opened  successively  from  the  top  downward 
to  control  the  air  pressure  required  for  the 
var3'iDg  heights  of   the  water  in   the  well, 
which  in  most  wells  varies  greatly  with  the 
quantity  pumped.      By  this  device,  which  is 
operated  b}^  the  valve  wheel  at  the  top 
of  the  well  pipe,  the  best  point  of  sub- 
mersion of  the  air  pipe  for  the  most  eco- 
nomical use  of  air  required  for  the  vary- 
ing height   of  the  water  level   in    the 
well  and   the    height  to 
which    the    water    is    to 
be  pumped,  is  obtained. 
The  section   to   the   left 
in  Fig.  506  shows  a  dou- 
ble-tube   well ;     the  sec- 
tions   are    self-explana- 
tor5^ 


COMPRESSED    AIR    WORK. 


723 


Fig.   506.— AIK-LIFl'    I'UMP   OF  THE   PNEUMATIC  ENGINEERING  COMPANY, 


Fig.    507.  — a  LINE   OF  WELLS  OPERATED  BY    COMPRESSED  AIR. 


724 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


Fig.  507  is  a  scenic  view  of  a  system  of  air-lift  gang  wells 
discharging  into  the  funnels  of  an  underground  conduit  hav- 
ing a  gravity  flow  to  a  basin  from  which  the  water  may  be 
pumped  to  a  high  reservoir. 

A  direct  system  of  pumping  water  by  compressed  air  under 
the  patents  of  Prof.  E.  G.  Harris  is  operated  by  this  company. 

The  name  "direct  air- 
pressure  pump  "  is  applied 
to  that  class  of  pumps  in 
which  the  liquid  is  taken 
into  an  air-tight  vessel  and 
then  driven  out  by  the  ap- 
plication of  compressed  air 
directly  to  the  surface  of 
the  liquid.  For  instance, 
if  the  vessel  B  (Fig.  508) 
contains  water,  and  air  be 
forced  in  through  the  pipe 
C,  the  water  will  be  driven 
out  through  the  pipe  A. 
The  apparent  simplicity  of 
this  operation,  and  the  ab- 
sence of  costly  cylinders, 
pistons,  rods,  valves,  etc., 
have  made  it  a  popular 
means  of  water  supply  with  various  modifications.  This  system 
is  not  a  new  one,  having  been  patented  by  Upham  in  1809,  and 
the  system  in  its  duplex  form  was  patented  in  England  in  1865. 
The  apparent  difficulty  in  the  use  of  this  system  lies  in  the 
loss  of  power  when  the  compressed  air  in  B,  after  driving  the 
water  out  of  the  vessel,  is  allowed  to  escape  into  the  atmos- 
phere, thus  losing  all  the  power  that  was  required  to  compress 
the  air.  The  percentage  of  this  loss  increases  with  the  head 
against  which  the  water  is  pumped,  and  is  about  50  per  cent 
when  pumping  to  a  height  of  100  feet. 


Fig.  508.— direct-pressure  system. 


COMPRESSED   AIR    WORK. 


725 


PV/\T£:iS 


In  the  following  system,  the  above  difficulties  are  overcome 
to  a  degree  that  cannot  be  surpassed ;  for  in  it  there  are  no 
floats  and  the  air  is  )wt  al/ozvcd  to  escape,  being  used  over  and 
over  so  that  none  of  the  work  done  on  it  is  directly  lost. 

Fig.  509 
shows  how  the 
above  c  o  n  d  i  - 
tions      are      at- 

tained.       S  u  p  - 

pose  the  compressor  to  be  m  operation 
with  switch  set  as  in  the  figure ;  the  air  will 
be  drawn  out  of  the  right-hand  tank  and  forced 
into  the  left-hand  tank ;  and  in  so  doing  will 
draw  water  into  the  former  and  force  it  out  of 
the  latter.  The  charge  of  air  in  the  system 
is  so  adjusted  that  when  one  is  emptied  the 
other  is  just  filled.  At  that  moment  the  switch 
will  reverse  the  pipe  conditions  so  that  action 
in  the  tanks  wall  be  reversed. 

The  automatic  control  of 
the  action  of  the  pump  is  made 
by  an  air  switch  at  the  com- 
pressor, which  is  thrown  by 
the  differential  pressure  in  the 
air  pipes.  The  change  in  the 
pressure  of  these  pipes  alter- 
nating between  the  hydrostatic 
pressure  in  the  air  force  pipe 
and  the  absolute  pressure  in  the  air  suction  pipe  is  equal  to  the 
head  of  water  in  the  tank  above  the  w^ater  level  in  the  well. 
At  the  moment  of  the  greatest  difference  in  pressure  in  the  air 
pipes,  the  automatic  switch  reverses  the  connections,  and  the 
compressor  draws  the  air  from  the  empty  chamber  and  forces 
it  into  the  full  chamber.  The  compression  and  expansion 
nearly  balance  each  other,  and  there  is  but  little  loss  in  powder. 


W 


i^Tjs 


Pu/^f>  Tanks 


WATCR  SUPPLY 


Fig.  509.— duplex  automatic  water  lie 


726 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


The  same  system,  as  shown  in  Fig.  510,  may  be  operated  as 
a  two-stage  or  compound  water  lift  by  placing  one  of  the  cham- 
bers in  the  well  or  sump  and  discharging  its  water  into  a  sump 
or  open  tank  at  a  higher  level.  They  may  be  operated  alter- 
nately as  before,  and  thus  be  made 
to  raise  one-half  the  volume  of 
water  to  double  the  height,  or 
raise  one-half    the  volume  to  the 


Switch 
Automatic 
Air 


iL, 


Fig.  510.— iwo- 

STAGF.    AIR-LIFT 
PUMP. 


same  height  with  one-half  the  air  pressure. 

The  size  of  air  pipes  in  this  system  re- 
quires a  somewhat  complex  adjustment  in  re- 
lation to  the  size  of  the  water  chambers  and 
the  height  of  the  water  lift,  as  well  as  the 
distance  of  the  compressor  from  the  chambers, 
for  the  best  econom}' ;  the  work  of  compression  and 
expansion  in  the   air    pipes    being    an    absolute    loss 

r—  subject  to  economical   adjustment   for   least  friction, 

while  the  compression  and  expansion  in  the  displace- 
ment chambers  are  a  necessary  loss  to  meet  the 
hydrostatic  conditions  of  the  height  to  which 
the  water  is  raised. 
Its  efficiency  is  due  to  the  well-balanced  condition  of  the 
pumping  plant,  including  the  compressor,  sizes  and  length  of 
air  and  water  pipes,  that  the  friction  maybe  a  minimum  for  the 
quantity  of  water  to  be  pumped.  Under  the  best  conditions, 
an  efficiency  of  65  per  cent  of  the  indicated  work  of  the  com- 
pressor may  be  expected  at  75  pounds  air  pressure,  pumping 
water  to  a  possible  height  due  to  that  pressure,  and  varies  in- 
versely with  the  height  and  pressure. 

The  principle  of  the  direct  air-lift  pump  with  discharge  of 
air  at  each  stroke  is  illustrated  in  Fig.  512  by  one  of  the  earlier 
methods  of  operating  the  air  valve  by  a  float,  which  was  placed 
on  the  outside  of  the  chamber  and  connected  with  the  top  and 
bottom  of  the  chamber  by  a  flexible  tube ;  so  that  the  float, 
alternately  filled  with  water  or  air  by  hydrostatic  equilibrium 


COMPRESSED   AIR    WORK. 


727 


through  the  flexible  tube  connection,  was  raised  at  the  moment 
of  full  discharge  of  water  from  the  chamber,  throwing  the  air 


Fig.  5II.~1'HE    AUTOMAIIC  SWITCH   OF  THE   HARRIS  SYSTEM. 


valve  open  to  the  exhaust  and  closing  the  air  inlet.  The  water 
rising  in  the  chamber  filled  the  float  at  its  upper  position,  when 
it  fell  by  its  weight,  fully  opening  the  inlet  air  valve  and  clos- 
ing the  exhaust.  A  flap  valve  on 
the  bottom  of  the  chamber  admit- 
ted the  water  by  gravity.  This 
system  has  been  modified  in  vari- 
ous ways  by  rods  directly  connected 
to  the  air  valve  and  a  sliding  float 
within  the  chamber,  one  form  of 
which  is  illustrated  in  Fig.  513,  in 
the  Halsey  pneumatic  pump,  which 
consists   of    a   tank    submerged    in 

,  ,  ,1  ,..-,.  Fig.  512.— float-governed  air-lift 

the    water    or    other    liquid    to    be  pump. 


72  8 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


pumped.  From  the  air  valve  contained  in  the  top  casting  a 
rod  descends  through  the  tank,  having  a  float  upon  it,  this  float 
being  an  inverted  bucket  of  sheet  metal.  The  water  flows  into 
the  tank  when  the  air  exhaust  is  open,  the  inverted  bucket  rid- 
ing on  top  of  the  water;  and  when  full  the  bucket  engages  with 


Fig.    513.— the    llALSEY  DIRECT-AIR-PRESSURE   PUMP. 


a  collar  on  the  top  of  the  rod  liftmg  the  same,  opening  the  air 
valve  and  closing  the  exhaust.  The  air  is  thus  admitted  di- 
rectly to  the  surface  of  the  water  and  forces  it  out.  As  the 
water  level  descends  the  bucket  at  the  lower  end  becomes  un- 
covered ;  its  weight  pulls  down  the  rod  and  reverses  the  valve, 
thereby  discharging  the  air,  when  the  operation  is  repeated. 
We  should  say  that  the  rod  described  also  operates  a  supple- 


COMPRESSED    AIR   WORK. 


729 


^^ 


mentary  valve  which  turns  the  air  into  one  or  the  other  end  of 
the  main  valve-chest  precisely  like  a  common  steam  pump.  It 
is  plain  that  the  machine  is  entirely  automatic  and  extremely 
simple,  and  adapted  to  a  very  wide  range  of  uses.  It  is  part  of 
the  Pneumatic  Engineering  Company's  pumping  system. 

In  the  Clayton  patent  lately  issued,  a  sealed  float  rises  and 
falls  on  a  rod  with  stops  to  operate  the 
air  valve. 

A  combination  of  the  direct-acting 
tank  system  and  the  Pohle  expansion  air 
lift  has  been  devised  by  Mr.  Wheeler,  by 
which  the  high-lift  system  maybe  utilized 
from  a  shallow  sump  by  raising  the  water 
about  one-half  the  height  by  direct  press- 
ure, then  injecting  air  under  the  water 
colunir  from  the  same  air  pipe  used  for 
the  direct  lift,  and  thus  doubling  its  ele- 
vation. In  Fig.  514  is  shown  a  sec- 
tional elevation  of  this  system,  in  which 
A  is  the  direct  pressure  or  displacement 
chamber,  from  which  the  water  is  raised 
to  a  height  at  C  ;  air  is  injected  at  B,  and 
by  its  lifting  and  expanding  action  com- 
pletes the  lift;  the  pressure  in  the  cham- 
ber A  being  equivalent  to  the  deep  immer- 
sion required  in  the  Pohle  system.  This  system,  as  shown  in 
the  figure,  is  alternating,  and  evidently  could  not  run  constantly 
with  one  chamber;  but  by  making  a  double-chambered  direct 
lift  as  in  Fig.  518,  and  connecting  the  air  pipe  to  the  water 
column  direct  from  the  pressure  side  of  the  air  compressor,  and 
using  the  air  switch  only  on  the  direct-lift  pipes,  a  continuous 
flow  would  be  obtained. 

The  efficiency  of  the  Wheeler  pneumatic  pump  just  de- 
scribed compares  very  favorably  with  any  of  the  other  methods  of 
pumping  by  air  pressure.     In  a  series  of  tests  made  by  Mr.  H. 


Fig.  514. —combined   air- 
lift PUMP. 


730 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


C.  Behr,  published  in  Couiprcsscd  Aii\  the  computed  effi- 
ciencies under  varying  conditions  of  air  pressure  of  from  19  to 
41  pounds  per  square  inch  for  a  lift  of  105  feet  from  a  shallow 
sump,  as  shown  in  Fig.  5 14,  were  from  24  to  48  per  cent  of  the 
least  work  needed  from  the  compressor,  or  from  1 7  to  30  per 
cent  including  the  efficiency  of  the  compressor. 


COMPRESSED-AIR      PUMPS      OF      THE      MERRILL      MANUFACTURING 
COMPANY,    x\EW    YORK    CITY. 

We  illustrate  in  the  following  figures  the  automatic  com- 
pressed-air system  of  the  above-named  company,  who  are  operat- 
ing under  the  patents  of  ]Mr.  F.  H.  Merrill.  By  this  system  air 
ma\'  be  compressed  at  any  available  distance  from  a  well  or 
water  supply,   and    perform   its   whole  duty,   save  friction,   in 

pumping  water  to  any  re- 
quired height  or  into  hori- 
zontal mains  to  distant  res- 
ervoirs. 

The  apparatus  consists 
of  one  or  two  water  cham- 
bers, adapted  to  be  sub- 
merged at  the  source  of 
water  supply,  and  an  auto- 
matic air  valve  located 
above  the  water  and  con- 
nected with  the  chambers 
by  one  or  two  air  pipes. 
The  automatic  air  valve  di- 
rects compressed  air  to  and 
from    the  water    chambers. 

Fig.  515.— si.\gle-.\cting  pu.mp.  .  .  .    .       -  ^         .        , 

from  which  the  water  is  al- 
ternately discharged  by  the  direct  action  or  displacement  of 
the  compressed  air,  without  the  intervention  of  pistons  or 
other  complicated  mechanism. 


COMPRESSED    AIR    WORK. 


731 


exijfiWT 


Fig.  516.— au  tomatic  air-valve  head. 


By  the  duplex  arrangement  of  chambers  a  perfectly  steady 
discharge  is  obtained. 

The  automatic  air  valve  (Fig.  516)  is  by  far  the  most  impor- 
tant part  of  the  apparatus.  This 
device  is  a  remarkably  simple  and 
ingenious  mechanism,  self-con- 
tained and  certain  in  its  action. 
It  is  actuated  solely  by  compressed 
air  applied  on  differential  surfaces, 
and  is  entirely  independent  of  the 
water  chambers.  The  valve  head 
contains  a  double-disc  differential 
air  valve,  which  is  operated  in  one 
direction  by  compressed  air  through 
a  small  valve  port  opened  by  a  water  float  in  the  under  sec- 
tion of  the  valve  head,  and  in  the  opposite  direction  b}'  a 
spring.  The  water  enters  by  a  pipe  connection  with  the  main 
discharge  pipe  and  is  released  by  the  air  when  the  water  in 
the  pump  chamber  falls  to  the  discharge  valve  by  the  uncover- 
ing of  a  supplementary  pipe 
connected  with  the  float 
chamber.  The  throw  of  the 
differential  valve  operates  a 
piston  valve  to  change  the 
flow  of  compressed  air  alter- 
nately from  one  cham.ber  to 
the  other,  and  also  alter- 
nates the  exhaust. 

The  single  chambers  are 
made  for  capacities  of  25 
and  50  gallons  per  minute. 

In  Fig.  517  is  shown  the 
internal  construction  of  the 
water  chamber  with  the  inlet 
and  discharge  water  valves.  pic.  si^.-.section,  water  valves. 


732 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


In  Fig.  518  is  represented  the  larger  size  of  a  duplex  direct- 
acting  air  pump  having  a  capacity  of  from  200  to  350  gallons 
per  minute. 

With  this  class  of  water  lifts  it  is  not  necessary  to  place  the 
operating  valve  mechanism  near  the  water  chambers  as  repre- 


FlG.    518. -THE  DOUBLE-CHAMBERED  PUMP. 

sented  in  the  figures,  but  at  any  convenient  location  at  the  top 
of  the  well  where  it  can  be  easily  inspected;  then  there  will 
not  be  less  efficiency  of  the  pump  than  is 
due  to  the  volume  of  the  air  in  the  connect- 
ing pipes,  between  the  valve  and  chamber. 
A  differential  piston  air-lift  pump  (Fig. 
519)  is  made  by  this  company,  adapted  for 
light  duty  and  domestic  service,  and  is  de- 
signed for  pumping  from  driven  wells  or 
any  place  where  a  displacement  pump  cham- 
ber cannot  be  inserted  or  submerged. 

It  consists  of  two  brass  differential  cyl- 

FlG.  519 -DIFFERENTIAL  .,  -.  ..JTii  ij 

PISTON  PUMP.  mders,    having    connected    pliable    packed 


COMPRES=^ED    AIR    WORK. 


733 


differential  pistons,  and  an  air-pressure  controlling  valve  in 
the  head  of  the  larger  cylinder,  actuated  by  the  pistons  at  the 
extreme  end  of  their  strokes. 

This  little  pump  will  fill  the  requirements  of  many  light 
duty  cases,  using  compressed  air  furnished  by  an  air  compres- 
sor located  any  distance  away,  driven 
by  any  available  power — belt,  steam, 
electricity,  gas,  or  oil.  It  is  suitable  for 
any  suction  up  to  15  feet  and  for  50-feet 
lift. 

In  Fig.  520  is  shown  the  combination 
inductor  and  displacement  pump,  for 
use  in  bored  wells,  in  which  the  induced 
lift  on  the  principle  of  the  Pohle  air  lift 
raises  the  water  to  a  displacement  cham- 
ber in  a  pit  at  the  surface,  from  which 
it  is  raised  to  the  required  height  by 
direct  air  pressure. 

In  Fig.  521  is  shown  a  section  of  a 
gang  system  of  air-lift  wells  with  cen- 
tral displacement  pump. 

In  Fig.  522  is  shown  a  Merrill  water- 
pumping  system  for  service  where  it  is  necessary  that  the  valve 
mechanism  or  working  parts  be  placed  some  distance  from  and 
above  the  water  chambers,  as  in  the  case  of  rivers  v,'here  the  rise 
and  fall  of  water  are  great,  and  where  it  is  desired  to  have  the 
controlling  valve  above  high  water,  and  accessible  at  all  times. 

By  this  system  of  arranging  the  location  of  the  air  valve 
above  and  at  a  distance  from  the  location  of  the  well  or  intake, 
and  thus  facilitating  a  pure  water  supply  for  public  and  private 
use  by  locating  the  wells  in  the  filter  sands  of  streams  and 
water-courses  with  the  air  valves  on  the  bank  and  an  air-com- 
pressing station  at  any  convenient  distance,  a  valuable  water- 
supply  service  may  be  made  available  at  all  times  and  under 
any  condition  of  flood  that  would  otherwise  derange  the  old 


Fig.  520.— combination  i'l.mi'. 


734 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


systems  of  water  supply  from  rivers.  The  only  precaution 
necessary  would  be  to  build  the  well  curb  above  the  flood  line, 
or  cover  the  well  with  sand  and  carry  the  exhaust  pipe  up  the 
bank,  or  to  a  safe  place  out  of  flood-water  range.  In  this  man- 
ner the  neglected  and  scanty  water  supply  of  towns  and  fac- 
tories may  be  reinforced  with  the  pure  and  filtered  element  so 
essential  to  life  and  prosperity. 

Air  pressure  is  used  for  elevating  milk  in  dairies  and  for 
aerating  milk.     For  elevating,  the   milk   is  poured  into  large 


Fig.    521.-THE   GAXG   SVSTKM   OF   BORED   OR    DRIVEN   WELLS. 

In  combination  with  the  direct  air-pressure  lift.    By  this  method  a  settling-  basin  will  gather  the 
sand  from  the  bored  wells,  and  the  direct  displacement  pump  will  be  tree  to  pump  clear  water. 

cans,  the  top  closed  and  connected  with  an  air  pump.  A  pipe 
from  the  bottom  of  the  can  conveys  the  milk  under  air  pressure 
to  any  required  height  or  distance. 

Color  liquids  in  dye  houses  which  are  destructive  to  pumps, 
or  are  injured  by  contact  with  the  metals  of  pumps,  are  elevated 
or  discharged  at  various  points  through  pipes  suitable  for  the 
coloring  fluids,  by  direct  air  pressure. 


COMPRESSED    AIR    WORK. 


735 


In  chemical  works  the  same  system  of  transfer  of  acids  is 
used. 

The  manufacture  of  sulphuric  acid  is  a  compressed-air  proc- 
ess in  which  the  large  condensing  chambers  are  dispensed  Avith 
and  the  process  is  made  more  direct  and  compact.  The  sulphur 
is  burned  under  air  pressure  in  an  air-tight  furnace,  and  by  the 


FRONT  ELEVATION  OF  PNEU.  PUMP, 


SIDE  ELEVATION  OF  PNEU.  PUMP. 


Fig.  522.— the  .merrill  pneumatic  pump. 
Direct  acting,  with  elevated  air  valves. 


same  pressure  the  products  of  combustion  are  forced  through 
pipes  beneath  water  in  a  closed  tank,  rising  in  bubbles,  and  so 
on  through  a  series  of  tanks,  until  the  entire  acid  product  is 
absorbed. 


ECONOMY    OF    COMPRESSED    AIR    IX    PUMPING. 

Fig.  523  represents  what  has  been  termed  the  endless  chain 
of  pneumatic  power,  by  which  a  volume  of  air  is  compressed, 
transmitted  to  a  pump  or  motor,  does  work,  is  exhausted  into 
a  return  pipe,  and  retransmitted  to  a  low-pressure  receiver  at  a 


71^ 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


low  temperature,  and  again  compressed  to  the  proper  working 
pressure  for  another  round  in  this  cycle  of  air  work.  It  has 
been  in  use  in  California  for  several  years  with  success  for 
pumping  and  drilling,  and  is  known  there  as  the  "  Cummings 
process  "  oi  system. 

The  economy  of  this  system  is  most  apparent  in  eliminating 
frost  at  the  exhaust  and  the  conservation  of  heat.     The  mois- 


Fig.  523.— the  endless  chain  in  compressed-air  work. 


ture  in  the  air  is  soon  condensed  and  deposited  in  the  low-press- 
ure cold-air  receiver,  when  the  system  becomes  a  dry-air  one, 
and  may  be  operated  as  a  dense-air  system  by  which  the  adia- 
batic  losses  are  lessened  by  operating  on  the  greater  curve  of 
heat  expansion  and  contraction  due  to  higher  pressures  as  well 
as  the  less  differentiation  of  volumes  at  the  higher  pressures. 
This  singular  property  of  compressed  air  is  graphically  illus- 
trated in  the  diagram  (Fig.  45).  It  is  also  in  use  in  the  Allan 
dense-air  refrigerating  machine. 

The  economies  of  this  system,  due  to  working  pumps  and 


COMPRESSED   AIR   WORK.  737 

drills  or  motors  that  carry  full  pressure  nearly  to  the  full  stroke, 
have  been  worked  out  by  Mr.  A.  E.  Shodzko,  who  has  found 
an  efficiency  of  .69  with  working  pressures  of  200  and  100 
pounds  in  the  two  pipes,  as  against  .33  in  the  single-pipe  sys- 
tem, as  ordinarily  used,  as  between  the  compressor  and  motor. 
With  reheating  the  efficiency  is  increased  in  this  system  to  a 
possible  85  per  cent.  In  ordinary  pressures  used  in  mining 
machinery,  say  up  to  90  pounds,  and  exhausting  into  the  return 
pipe  at  30  pounds  pressure,  the  continued  operation  will  work 
under  a  temperature  cycle  of  200°  F.,  while  in  the  single-pipe 
system  with  open  exhaust  the  working  cycle  is  about  300°  F. 
under  the  same  operative  pressure. 

The  claim  for  efficiency  and  practicability  for  this  system 
seems  to  have  been  criticised  by  assuming  that  the  motor, 
pump,  or  drill  must  be  operated  at  full  pressure  for  the  full 
stroke ;  but  this  claim  is  not  reasonable,  for  the  possibilities  of 
expansion  between  the  initial  pressure  in  the  flow  pipe  and  the 
pressure  in  the  return  pipe  only  involves  the  air  friction  in  the 
two  pipes,  leaving  a  considerable  margin  for  expansion  econ- 
omy in  motors ;  but  this  principle  cannot  be  applied  to  rock  drills 
and  hoisting  engines  further  than  their  fixed  cut-off. 

COMPRESSED    AIR    FOR    LIFTING    SEWAGE. 

The  Shone  system  as  used  in  England  is  illustrated  in  a  ver- 
tical view  of  the  air  lift  in  Fig.  524  and  a  plan  in  Fig,  525,  which 
represents  the  sewerage  system  in  the  city  of  Norwich,  Eng- 
land. The  old  works  were  subject  to  floods  in  the  lower  part  of 
the  city  ;  by  the  apparatus  shown  in  the  illustration  the  old  sewers 
were  intercepted  at  five  points  near  the  river,  and  water  lifts  by 
direct  air  pressure  were  located  to  lift  the  sewage  from  15  to  2  i 
feet  in  different  localities  to  a  main  outfall  sewer  that  discharged 
at  a  distant  pumping  station,  from  which  it  is  pumped  to  a 
sewage  farm.     A  pair  of  turbine  wheels  at  the  dam  above  the 

town  operate  the  compressors  at  18  pounds  pressure,  which  dis- 

47 


738 


COMPRESSED    AIR   AND    ITS    APPLICATIONS. 


charge  C50    cubic  feet  free  air  per  minute  into  two  large  re- 
ceivers, from  which  the  compressed  air  is  distributed  through 


:W 


Fig.  524.— elevation  of  sewage  lift. 


underground  mains  to  the  different  lift  stations.  Each  station 
is  provided  with  two  air-lift  chambers  with  floats  and  trip  valves 
or  rods  to  operate  the  air  valves.     The  ejector  chambers  vary 


Fig.  525.— plan  of  sewage  lift. 


COMPRESSED    AIR    FOR    PURIFYING    WATER.  739 

in  size  at  the  different  stations  to  meet  the  variation  in  sewage 
flow  from  the  districts  converging  at  each  station,  ranging  in 
cubic  contents  from  300  to  2,000  gallons. 

The  automatic  pneumatic  cesspool  drainage  is  extensively 
in  use  in  the  United  States.  Its  convenience  and  value  from  a 
sanitary  point  of  view  cannot  be  overrated.  A  simple  form  of 
this  device  is  in  operation  at  La  Crosse,  Wis.,  to  clear  the  pits 
of  a  round-house;  consisting  of  a  large  tank  in  a  catch-basin, 
in  which  a  float  slides  upon  a  rod  between  stops  that  opens  a 
three-way  valve  in  an  air-pressure  pipe  which  discharges  the 
vater  to  a  higher  level  sewer,  the  water  flowing  into  the  tank 
by  gravity  through  a  flap  valve  on  the  release  of  the  air  press- 
ure through  the  action  of  the  float  and  valve. 

AERATION    OF   WATER   BY    COMPRESSED    AIR. 

It  is  well  known  now,  among  hydraulic  engineers,  that  an 
ample  aeration  of  water  in  tanks  and  reservoirs  will  prevent 
stagnation,  check  the  growth  of  algae,  remove  the  disagreeable 
odor  from  decomposing  vegetable  matter,  and  deposit  the  salts 
of  iron  that  sometimes  pervade  waters  from  iron  soils  or  that 
have  traversed  long  lines  of  iron  pipe.  Fig.  526  represents  the 
pipe  plan  for  aerating  a  tank  62  feet  in  diameter,  59  feet  high, 
holding  1,300,000  gallons,  at  Brockton,  Mass. 

In  the  bottom  of  the  tank  are  three  2-inch  galvanized  iron 
pipes  which  radiate  from  a  point  near  the  side  as  shown.  The 
centre  arm  is  56  feet  long,  and  the  two  side  arms  47  feet. 
Spreading  out  from  these  pipes  are  thirty-nine  brass  tubes  one- 
quarter  inch  in  diameter,  except  five  long  branches  from  the  cen- 
tre arm,  which  are  three-eighths  inch  in  size. 

The  small  pipes  are  perforated  at  distances  of  3  feet  with 
■^-inch  holes,  and  are  supported  on  iron  chairs  which  hold  them 
clear  of  the  bottom.  The  2-inch  pipes  are  carried  through  the 
supply  pipe  from  the  pump,  and  furnished  with  valves  to  con- 
trol the  flow  of  air.      They  are  finally  connected  with  a  2-^-inch 


740 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


pipe  from  the  pumping  station,  which  is  provided  with  a  check 
valve  to  prevent  water  from  going  to  the  pump.  The  air  is 
supplied  by  a  7!  X  9  X  9  inch  Clayton  duplex  compressor,  fur- 
nishing 172,000  cubic  feet  of  air  in  twenty-four  hours.  The  air 
is  forced  directly  into  the  tank,  no  receiver  being  used.  By 
this  means  the  water  is  thoroughly  agitated  and  aerated,  doing 
away  with  its  former  odors  and  taste. 

Another  method  of  aeration  of  water  is  by  pumping  air  di- 
rectly into  the  main  between  the  intake  and  the  reservoir,  and 

into  the  delivery  main  from 
a  reservoir. 

In  another  case,  in  order 
to  improve  a  supply  drawn 
from  a  lake  in  which  algae 
had  given  some  trouble,  a 
1 2 -inch  pipe  was  laid  from 
the  gate  house  at  the  lake 
for  a  distance  of  350  feet  to 
within  50  feet  of  the  lowest 
part  of  the  main.  At  this 
point  a  small  Clayton  com- 
pressor, driven  by  a  lo-inch 
double-discharge  turbine,  was  set  up.  This  plant  required 
259,000  gallons  of  water  in  twenty-four  hours  to  force  82,250 
gallons  of  air  into  the  200,000  gallons  of  water  supplied  to  the 
town  from  the  lake.  When  the  water  was  turned  on  to  the 
wheel,  the  air  was  forced  into  the  main  against  the  flow  in  the 
pipe  and  rose  toward  the  lake,  coming  up  through  the  gate 
house  in  great  volumes  and  agitating  the  water  with  consider- 
able violence,  so  that  it  immediately  lost  its  taste  and  odor. 
The  pressure  of  the  air  as  delivered  from  the  compressor  was 
20  pounds  per  square  inch.  In  this  connection,  attention  is 
called  to  the  aerating  plant  at  Charleston,  S.  C,  where  equal 
satisfaction  has  followed  the  adoption  of  this  method  of  puri- 
fication.     Every  practical  superintendent  and  engineer  who  has 


Fig.  526.— water-tank  aeration. 


COMPRESSED    AIR    FOR   PURIFYING   WATER.  74 1 

had  any  extended  experience  with  aeration  seems  to  favor  it, 
as  far  as  we  have  been  able  to  learn.  As  the  subject  now  stands, 
it  is  pretty  generally  admitted  that  aeration  will  prevent  stag- 
nation, check  the  growth  of  algae,  remove  disagreeable  gases, 
and  deposit  the  salts  of  iron  that  sometimes  occur  in  a  ground 
water,  although  it  has  yet  to  be  proved  that  it  will  hasten  the 
oxidation  of  organic  matter. 

Water  in  its  natural  state  is  never  found  chemically  pure ; 
matter  more  or  less  foreign  is  identified  with  it  and  detected 
under  the  test  of  the  chemist.  Nevertheless,  waters  thus  found 
are  fit  for  human  consumption,  and,  taken  from  nature's  labora- 
tory, are  pure  enough  for  general  use. 

The  methods  adopted  for  purifying  water  are  oxidation  or 
aeration  and  filtration.  Nature  herself  practises  and  carries 
on  successfully  the  process  of  purification.  When  her  adminis- 
tration is  interfered  with  by  man's  construction  of  dams  and 
reservoirs  to  confine  her  waters,  it  then  becomes  necessary  for 
him  by  mechanical  means  to  imitate  her  example.  In  this 
attempt  he  must  recognize  her  laws.  Oxidation  or  aeration  is 
one  of  nature's  processes  carried  on  successfully  for  the  purifi- 
cation of  water.  The  oxygen  is  dissolved  in  the  water,  coming 
in  contact  with  whatever  organic  matter  may  be  associated  with 
the  water,  changing  it  into  nitrites  and  carbonic  acid.  The 
greater  the  agitation  of  the  waters,  the  greater  the  beneficial 
changes  thus  wrought. 

Cascades,  fountains,  the  introduction  of  air  to  conduits,  arti- 
ficial falls,  thin  films  of  water  passing  over  large  surfaces — in 
fact,  any  device  that  will  permit  the  air  to  mingle  with  the 
waters — give  new  life  to  the  waters  and  death  to  organisms. 
The  plan  adopted  by  the  Utica  (N.  Y.)  Water  Company  is  on 
the  fountain  principle,  discharging  the  water  under  pressure 
through  a  series  of  pipes,  the  aggregate  areas  presumably  equal 
to  the  main  discharge  pipe,  and  into  a  shallow  basin.  The 
greater  the  pressure  the  greater  the  height  the  waters  are 
elevated  by  their  several  columns,  giving  proportionately  time 


742 


COMPRESSED    AIR    AND    ITS   APPLICATIONS. 


for  the  action  of  the  air  on  the  ascending  and  descending  waters. 
It  occurs  to  one's  mind,  however,  that  the  quantity  of  water 
thus  treated  should  not  be  in  excess  of  the  daily  amount  used, 
that  each  day's  supply  of  water  should  be  fresh.  This  mode 
of  purification  of  water  will  require  treating  reservoirs  of  shal- 
low depth  and  surface  area  equal  to  requirements. 

A  similar  plan  to  the  Utica  plant  is  the  one  at  Fresh  Pond, 
adjacent  to  the  Stony-brook  reservoir,  at  Cambridge,  Mass. ; 
different  in  that  four  outlets  of  discharge  are  in  use,  and  throw- 
ing the  water  into  the  air  40  feet  above  its  outlet. 

THE  PNEUMATIC  CYANIDE  PROCESS  FOR  THE  EXTRACTION  OF 

GOLD. 

The  features  of  the  "  pneumatic  "  process  are  so  easily  un- 
derstood that  it  does  not  require  an  expert  or  a  thorough  chem- 
ist to  appreciate  them,  for  every  mining  man  has  had  more  or 
less  experience  with  compressed  air.  and  most  of  them  know 
something  about  the  cyanide  process  and  understand  that  oxy- 
gen is  absolutely  necessary  in  a  solution  of  cyanide  of  potassium 
in  order  to  form  a  new  compound,  cyanogen,  which  is  the  true 


Fig.  527 —series  of  leaching  vats,  or  tanks,  fitted  with  pipes  and  valves  fok  the 
introduction  and  conl  rol  of  the  compressed  aik. 


solvent  of  the  gold.  They  know  also  that  agitation  hastens  the 
process  of  dissolving  and  extracting  the  gold  values  during  the 
leaching  process,  because  agitation,  or  stirring,  enables  the  oxy- 
gen of  the  air  to  reach  the  solution  more  rapidly  to  form  cyano- 
gen and  also  to  bring  the  ore  and  solution  into  more  intimate 
contact,  and  does  in  a  few  hours  what  it  takes  days  to  do  if  the 
ore  and  solution  remain  unmoved  in  the  leaching  vats. 

Many  attempts  have  been  made  to  stir  or  agitate  the  mass 


COMPRESSED    AIR    IN   THE    CYANIDE    PROCESS. 


"43 


of  leaching  ore  by  machinery ;  but  the  great  costs  of  power,  ex- 
pensive construction,  breakage  of  parts,  etc.,  have  caused 
them  to  be  abandoned,  and  mill  owners  have  gone  back  to  the 
old  slow  process  of  letting  the  ore  stand  for  days  in  the  leaching 
vats  because  there  was  no  practical  and  cheap  way  of  agitating 


Fig.  578.— section  through  the  lf.achixg  vats. 

Showing-  the  air  pipes  under  the  perforated  bottom  and  the  double  trap-door  in  the  bottom 
for  discharging  the  leached  refuse. 

them,  or  of  getting  the  oxygen  through  the  solution,  except  by 
the  slow  absorption  from  the  atmosphere. 

Just  at  this  time,  when  it  seemed  as  if  improvement  in  the 
cyanide  process  was  at  a  standstill,  the  "  pneumatic "  process 
comes  forward  with  a  method  so  simple  and  so  effective  that  it 
is  a  wonder  that  it  was  not  thought  of  sooner. 

It  is  simply  the  introduction  of  strong  currents  of  com- 
pressed air  into  the  bottom  of  the  leaching  vats,  which  force 
their  way  upward  bubbling  and  boiling  through  the  mass  of 
crushed  ores  and  cyanide  solution,  and  thus  furnish  both  the 
oxygen  and  the  agitation  needed  for  the  rapid  and  thorough 
extraction  of  the  gold.  This  method  of  forcing  the  air  through 
the  leaching  ores  can  be  readily  understood  by  means  of  the 
cuts  shown.  The  air  pressure  required  is  small;  no  more  than 
to  overcome  the  hydrostatic  pressure  of  the  liquid  and  keep  the 
air  bubbling  like  boiling  water.  Reheating  the  air  tends  to 
warm  the  liquid  and  to  facilitate  the  work.  It  amply  pays  for 
reheating  the  air. 

WOOD    VULCANIZING. 

The  process  of  vulcanizing  wood  by  the  Haskins  system  is 
about  as  follows :  Large  iron  or  steel  tanks  are  arranged  hori- 
zontally and  of  sufficient  size  to  admit  the  charge  of  wood  re- 
quired to  be  vulcanized. 


744  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

Coils  of  pipe  are  placed  inside  the  tanks  for  the  purpose  of 
heating  the  air  to  the  desired  temperature  of  about  285°  to  300° 
F.  The  heating  is  usually  done  by  steam.  The  wood  is  placed 
inside  the  pipe-lineJ  tanks  and  steam  is  turned  on  until  the 
interior  is  heated  to  about  200°  F.  Then  the  openings  are 
closed  and  compressed  air  is  admitted  up  to  150  or  200  pounds 
pressure.  The  air  is  kept  circulating  around  the  wood  at  an 
average  heat,  the  desired  temperature  being  285°  to  300°  F. 
for  eight  or  ten  hours.  The  circulation  is  accomplished  by 
means  of  a  circulating  engine  which  takes  the  air  out  of  the 
vulcanizing  tank,  passes  it  through  a  reheater  and  back  to  the 
tank.  This  process  prepares  the  wood  in  such  a  way  that  it 
will  last  almost  indefinitely. 

AGING   OF    LIQUORS. 

The  purifying  of  alcoholic  liquors  is  accomplished  by  com- 
pressed air  through  the  Gushing  process,  w'hich  has  been  in 
vogue  for  many  years.  The  liquor  is  placed  in  receptacles  for 
the  purpose,  and  air,  after  it  has  been  washed  and  purified  by 
Professor  Tyndall's  well-known  method,  is  compressed  and 
forced  through  perforated  pipes  entering  the  liquor  in  minute 
streams.  The  liquid  is  violently  agitated  and  the  air  permeates 
every  portion  of  it.  The  air  being  warm  oxidizes  the  fusel  oil 
and  at  the  same  time  volatilizes  and  expels  into  the  open  air 
the  light  poisonous  ethers,  leaving  the  liquors  thoroughly  pure 
and  free  from  aldehydes.  It  is  claimed  that  by  this  process 
new  liquor  for  medicinal  purposes  is  made  practically  as  good 
as  old,  and  that  the  drinking  of  liquor  treated  thus  does  not 
cause  stupefaction,  headaches,  and  other  disagreeable  results. 


Chapter  XXXIII. 


REFRIGERATION 


REFRIGERATION. 

REFRIGERATION   BY    THE   VACUUM    SYSTEM. 

This  is  generally  known  as  the  vacuum  process,  for  as  the 
refrigerating  agent  itself  is  rejected,  the  only  agent  of  a  suffi- 
ciently inexpensive  character  to  be  employed  is  water,  and  this, 
owing  to  its  high  boiling-point,  requires  the  maintenance  of  a 
high  degree  of  vacuum  in  order  to  produce  ebullition  at  the 
proper  temperature.  The  vapor  tensions  of  water  at  tempera- 
tures up  to  boiling-point  at  atmospheric  pressure  are  given  in 
Table  II.,  from  which  it  will  be  seen  that  at  32°  F.  the  tension 
is  only  0.089  pounds  per  square  inch.  In  ice-making,  therefore, 
a  degree  of  vacuum  must  be  maintained  at  least  as  high  as  this. 
The  earliest  machine  of  this  kind  appears  to  have  been  made 
in  1755  by  Dr.  Cullen,  who  produced  the  vacuum  by  means  of 
an  air  pump.  In  18 10  Leslie,  combining  with  the  air  pump  a 
vessel  containing  strong  sulphuric  acid,  for  absorbing  the  vapor 
from  the  air  drawn  over,  and  so  assisting  the  pump,  succeeded 
in  producing  an  apparatus  by  means  of  which  from  one  to  one 
and  one-half  pounds  of  ice  could  be  made  in  a  single  operation. 
Vallance  and  Kingsford  followed  later,  but  without  practical 
results ;  and  Carre  many  years  afterward  embodied  the  same 
principle  in  a  machine  for  cooling  and  for  making  small  quan- 
tities of  ice,  chiefly  for  domestic  purposes.  His  machine,  which 
is  still  sometimes  used,  consists  of  a  small  vertical  vacuum  pump 
worked  by  hand,  either  by  a  lever  or  by  a  crank,  which  exhausts 
the  air  from  the  carafe  or  decanter  containing  the  water  or 
liquid  to  be  frozen  or  cooled.  Between  the  pump  and  the  water 
vessel  is  a  lead  cylinder,  three-fourths  full  of  sulphuric  acid, 
over  which  the  air,  and  with  it  the  vapor  given  off  from  the 
liquid,  is  caused  to  pass  on  its  way  to  the  pump.     The  vacuum 


748  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

thus  produced  causes  a  rapid  evaporation,  which  quickly  lowers 
the  temperature  of  the  water ;  and  if  the  action  is  prolonged  for 
about  four  or  five  minutes,  the  water  becomes  frozen  into  a 
block  of  porous,  opaque  ice.  The  charge  of  acid  is  about  four 
and  one-half  pints,  and  it  is  said  that  from  fifty  to  sixty  carafes 
of  about  a  pint  each  can  be  frozen  with  one  charge.  So  long  as 
the  joints  are  all  tight,  and  the  pump  is  in  good  order,  this 
apparatus  works  well ;  but  in  practice  it  has  been  found  trou- 
blesome and  unreliable,  and  consequently  has  never  come  into 
anything  like  general  use. 

In  1878  Franz  Windhausen,  of  Berlin,  Germany,  brought 
out  a  compound  vacuum  pump  for  producing  ice  direct  from 
water,  on  a  large  scale,  without  the  employment  of  sulphuric 
acid;  and  also  an  arrangement  in  which  sulphuric  acid  could 
be  used,  the  acid  being  cooled  by  water  during  its  absorption 
of  the  vapor,  and  afterward  concentrated,  so  that  a  fresh  supply 
was  rendered  unnecessary.  This  apparatus  was  improved  on 
in  1880;  and  in  1881  a  machine  nominally  capable  of  producing 
1 5  tons  of  ice  per  twenty-four  hours  was  put  to  work  experi- 
mentally at  the  Aylesbury  Dairy  at  Bayswater,  England,  It 
consists  of  six  slightly  tapered,  ice-forming  vessels  of  cast  iron, 
of  circular  cross  section,  closed  at  their  bottom  ends  by  hinged 
doors  with  air-tight  joints,  into  which  water  is  allowed  to  flow 
through  suitable  nozzles,  the  cylinders  being  steam-jacketed  in 
order  to  allow  the  ice  to  be  readily  discharged.  The  upper 
parts  of  these  vessels  communicate  with  the  pump  through  a 
long  horizontal  iron  vessel  of  circular  section  containing  sul- 
phuric acid,  which,  when  the  machine  is  in  operation,  is  kept 
in  continual  agitation  b}'  means  of  revolving  arms.  The  acid 
vessel  is  surrounded  with  cold  water,  which  carries  off  most  of 
the  heat  liberated  during  the  absorption  of  the  vapor.  The 
pump  has  two  cylinders,  one  double-acting  of  large  size,  and  a 
smaller  single-acting  one.  The  capacities  of  these  cylinders 
per  revolution  are  as  62  to  i .  The  air  and  whatever  vapor  has 
passed  the  acid  are  drawn  into  the  large  pump,  which  partially 


REFRIGERATION.  749 

compresses  and  delivers  them  into  a  condenser.  Here  part  of 
the  vapor  is  condensed  by  the  action  of  cold  water,  the  remain- 
der passing  along  with  the  air  to  the  second  pump,  where  they 
are  compressed  up  to  atmospheric  tension  and  discharged.  The 
advantage  gained  by  the  use  of  a  compound  pump  is  due  to  the 
action  of  the  intermediate  condenser  and  to  the  compression 
being  performed  in  two  stages,  by  which  the  losses  from  the 
clearance  spaces  in  the  large  pump  are  rendered  much  less  than 
they  would  be  if  compression  to  atmospheric  pressure  were  ac- 
complished in  a  single  operation.  The  effect  of  the  pump  is 
said  to  be  such  that  a  vacuum  of  half  a  millimetre  of  mercury, 
or  about  0.0097  pound  per  square  inch,  can  be  continuously 
maintained ;  though  in  actual  work  about  2^  millimetres,  or 
0.0484  pound  per  square  inch,  is  as  low  as  is  necessary.  The 
concentration  of  the  acid  is  effected  in  a  lead-lined  vessel,  in 
which  is  a  coil  of  lead  piping  heated  by  steam,  the  pressure  in 
the  vessel  being  kept  down  by  means  of  an  ordinary  air  pump. 
No  acid  pump  is  needed,  as  the  transfer  from  one  vessel  to  an- 
other is  effected  by  the  pressure  of  the  atmosphere.  The  com- 
paratively cool  weak  acid  on  its  way  to  the  concentrator  is 
heated  in  an  interchanger  by  the  strong  acid  returning  from 
the  concentrator.  Six  blocks  of  ice,  each  weighing  about  560 
pounds,  are  formed  in  about  twenty  minutes  after  starting, 
The  charge  of  acid  is  said  to  serve  for  three  makings  of  ice, 
after  which  it  becomes  too  weak,  and  requires  to  be  concen- 
trated. 

The  water  being  admitted  into  the  ice-forming  vessels  in 
fine  streams  offers  a  large  surface  for  evaporation,  and  is  al- 
most immediately  converted  into  small  globules  of  ice,  which  fall 
to  the  bottom  and  become  cemented  together  by  the  freezing  of 
a  certain  quantity  of  water  that  collects  there.  This  water 
being  in  a  violent  state  of  ebullition,  the  ice  so  formed  is  not 
solid,  but  contains  spaces  or  blow-holes,  which,  as  soon  as  the 
block  is  discharged  from  the  vessel,  become  filled  with  air  and 
cause  opacity.     Several  attempts  have  been  made  to  produce 


750  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

transparent  ice  by  the  direct  vacuum  process,  but  so  far  with- 
out success.  Distilled  water,  or  water  deprived  of  air,  has  been 
tried,  and  hydraulic  pressure  has  been  used  for  compressing  the 
porous  opaque  blocks,  but  neither  plan  has  been  found  practi- 
cable commercially.  It  would  appear  that  the  only  way  to  make 
clear  ice  by  the  vacuum  process  is  by  forming  it  in  moulds, 
subjected  externally  to  the  action  of  brine  previously  cooled  by 
the  evaporation  of  a  portion  of  its  water.  The  cost  in  this  case 
would  necessarily  be  greater;  but  the  ice  would  be  solid  and 
transparent,  and  would  consequently  have  a  higher  commercial 
value.  The  latent  heat  of  liquefaction  of  w^ater  being  142.6°  F., 
the  total  heat  to  be  abstracted  in  order  to  produce  i  ton  of  ice 
from  I  ton  of  w^ater  at  60°  F.  is  382,144  F.  pound  units.  Tak- 
ing the  latent  heat  of  vaporization  of  water  at  32°  F.  to  be 
1,091.7,  it  is  obvious  that  350  pounds  must  be  evaporated  to  make 
the  ton  of  ice.  But  in  addition  the  sensible  heat  of  evaporated 
water,  which  entering  at  60°  would  leave  at  about  32°,  would 
have  to  be  taken  off ;  and  this  would  require  the  evaporation  of 
about  9^  pounds  more,  making  a  total  of  about  360  pounds, 
without  allowance  for  loss  by  heat  entering  from  wnthout,  which 
would  be  considerable.  The  total  water  actually  used  is  given 
by  Mr.  Piper  at  12  tons  per  ton  of  ice,  including  the  quantity 
required  for  cooling  purposes.  The  fuel  consumption  is  stated 
to  be  180  pounds  of  coal  per  ton  of  ice;  but  a  much  larger 
quantity  is  actually  required.  It  is  consumed  in  generating 
steam  for  driving  the  vacuum  pump  and  the  concentrator  air 
pump,  and  for  evaporating  the  water  absorbed  by  the  acid. 
According  to  Dr.  Hopkinson,  the  cost  of  making  i  ton  of  opaque 
ice  is  4^-.  (about  $1);  experience  has  shown  that  a  much  higher 
cost  is  required  to  cover  the  necessary  expenses  for  repairs  and 
maintenance.  Windhausen's  machine  has  not  met  with  any 
extended  application,  owing  no  doubt  to  the  opaque  and  porous 
condition  of  the  ice  produced  by  it,  and  to  the  large  and  cum- 
brous nature  of  the  plant,  which  must  doubtless  require  great 
care  and  supervision  in  working. 


REFRIGERATION.  75  I 

A  vacuum  apparatus  for  refrigerating  liquids  by  their  own 
partial  evaporation,  and  for  making  ice,  was  brought  out  in 
1878  by  James  Harrison  in  England.  Its  chief  feature  is  the 
revolving  cylinder  or  pump,  which  affords  a  simple  and  effi- 
cient means  of  exhausting  large  volumes  of  vapor  of  low  ten- 
sion, without  incurring  the  loss  from  friction  of  ordinary  piston- 
packings,  and  the  trouble  of  keeping  them  tight  and  in  good 
working  order,  while  at  the  same  time  the  first  cost  is  much 
reduced.  The  pump  consists  of  a  hollow  iron  cylinder,  revolv- 
ing on  a  horizontal  axis,  and  divided  into  compartments  by 
longitudinal  partitions  of  L  section.  It  is  partially  filled  with  a 
non-evaporable  liquid,  or  one  which  evaporates  only  at  a  tem- 
perature considerably  in  excess  of  that  at  which  the  refrigerat- 
ing liquid  is  evaporated,  and  which  is  also  chemically  neutral 
to  the  vapor  that  is  brought  in  contact  with  it.  In  practice, 
oil  is  the  liquid  used.  The  refrigerating  or  ice-making  vessels, 
of  any  convenient  form,  are  connected  by  a  pipe  with  one  end 
of  a  fixed  hollow  axle  on  which  the  cylinder  revolves;  and  in- 
side the  cylinder  another  pipe  rises  up  above  the  level  of  the 
liquid,  the  longitudinal  partitions  being  stopped  short  at  one 
end  to  enable  this  to  be  done.  The  compartments  move  round 
mouth  downward,  carr3angwith  them  the  vapor  with  which  they 
are  charged,  and  compressing  it  to  an  extent  measured  by  the 
distance  they  dip  below  the  surface  of  the  liquid;  until,  when 
the  lowest  position  is  approached,  the  compressed  vapor  is 
liberated,  and  rises  into  a  fixed  hood  near  the  centre,  in  com- 
munication with  a  second  hollow  axle  at  the  opposite  end  of  the 
cylinder  to  that  at  which  the  vapor  enters.  Through  this  sec- 
ond axle  the  compressed  vapor  passes  to  a  surface-evaporative 
conden.ser,  in  which  it  is  partly  condensed  by  the  combined 
action  of  direct  cooling  and  the  partial  evaporation  of  water 
trickling  over  the  surface;  the  water  of  condensation,  together 
with  any  air,  is  then  compressed  to  the  tension  of  the  atmos- 
phere by  a  small  pump,  and  discharged.  By  this  process  it  is 
expected  to  produce  opaque  ice  on  a  large  scale  at  a  cost  of 


752  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

about  25  cents  per  ton.  The  fuel  consumption  will  certainly  be 
very  small,  because  friction,  which  is  a  large  item  in  the  Wind- 
hausen  apparatus,  is  here  to  a  large  extent  eliminated.  There 
would  also  be  a  saving  of  all  the  fuel  used  in  concentrating  the 
acid,  and  of  much  of  the  water  required  for  cooling  purposes, 
besides  a  reduction  in  the  first  cost  of  the  plant  and  in  the  ex- 
pense of  maintenance. 

Although  for  nearly  a  half-century  much  attention  has  been 
given  to  the  subject  of  cooling  and  refrigeration  by  the  vacuum 
process,  it  has  not  proved  a  commercial  success ;  it  is  still  feasi- 
ble for  experimental  work,  and  claims  a  space  in  the  history 
of  air  work. 


COMPRESSED-AIR    REFRIGERATION. 

THE    EARLIEST    ICE    MACHINE. 

The  earliest  known  appliance  for  making  ice  by  compressed 
air  seems  to  have  been  invented  and  put  into  actual  practice 
by  Dr.  John  Gorrie,  of  New  Orleans,  La.,  whose  patent  dates 
May  6th,  185  i,  although  ice  was  actually  made  in  his  machine 
at  Apalachicola,  Fla.,  in  the  summer  of  1850. 

The  machine  consisted  in  its  essential  operating  parts  of  an 
air-compressing  cylinder  and  piston  operated  fromi  a  crank 
shaft  by  connecting  rods. 

A  small  injection  pump  operated  from  a  cam  on  the  main 
shaft  was  so  adjusted  as  to  inject  a  small  spray  of  cold  water  into 
the  cylinder  during  the  latter  part  of  compression  at  each  stroke 
of  the  piston,  thus  being  the  leading  practical  application  of 
the  injection  system  for  cooling  the  air  during  compression  ;  the 
compressed  air  and  injected  water  being  driven  together 
through  the  exit  valves  and  through  a  coil  of  pipe  immersed  in 
a  tub  of  cold  water,  to  the  receiver,  from  which  the  injected 
and  condensed  water  was  drawn  off  through  a  waste  cock  at  the 
bottom. 

On  the  same  platform  and  connected  with  a  crank  on  the 


REFRIGERATION. 


753 


main  shaft,  was  located  the  expansion  cylinder  with  its  piston 
and  connecting  rods. 

The  size  of  the  expansion  cylinder  was  made  somewhat 
smaller  than  the  compressor  cylinder,  to  compensate  for  the 
decreased  volume  of  air  due  to  the  difference  between  adiabatic 


Fig.  529 -the  gorrie  ice  machine. 


and  isothermal  values  in  compression  and  expansion  for  both 
cylinders. 

The  expansion  cylinder  was  also  provided  with  an  independ- 
ent injection  pump  operated  from  a  cam  on  the  main  shaft  by 
which   an   injection  of  a  non-freezing  liquid  (brine)  was  made, 

which,  by  the  convection  of  its  heat  to  the  cold  air,  becomes  a 
48 


754 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


cooling  medium,  and  was  carried  with  the  cold  air  through  the 
exit  valves  and  connecting  pipe  into  the  cold  reservoir  sur- 
rounding the  cylinder. 

The  expansion  cylinder  was  enclosed  in  a  brine  jacket  with 
outlets  for  the  cold  exhaust  and  injection,  through  pipes 
terminating  in  the  brine  vat,  for  the  purpose  of  utilizing  the 
refrigerating  effect  of  the  expanded  air  for  its  full  value ;  the 
free  air,  finally  permeating  the  ice-making  chamber  above,  and 
an  outer  insulating  case  surrounding  the  brine  tank  and  expan- 
sion cylinder,  made  its  exit  through  a  coil  in  an  insulated  tank 
for  cooling  the  water  to  be  frozen,  which  was  drawn  from  the 
cooling  tank  into  the  freezing  cans  of  the  form  much  in  the 
style  as  now  used,  and  placed  in  the  cold  brine  tank  for  the 
freezing  operation. 

It  may  be  seen  from  the  amply  illustrated  description  in  the 
patent  specifications,  and  from  the  testimony  of  persons  that 


Fig.  530.— front  elevation,  ice  machine. 


saw  the  apparatus,  that  Dr.  Gorrie  had  conceived  and  put  into 
practice  a  device  almost  perfect  in  principle  for  refrigeration 
by  compressed  air  at  least  a  score  of  years  before  it  became  a 
commercial  factor  in  any  form. 


REFRIGERATION. 


755 


The  idea  of  using  the  terminal  exhaust  for  cooling  the  water 
to  be  frozen  to  near  the  freezing-point  was  a  most  important 
one  in  the  matter  of  economy. 

The  whole  apparatus  as  completed  in 
1850   seems  to  have  been    the    result  of 
several  years  of  study  and    experiment, 
and  as  now  viewed  was  a  most  complete 
and    advanced    conception    of    the    later 
developments  of  refrig- 
eration   by    compressed 
air  as  made  by  Lightfoot, 
Hall,  Bell,  and  others  in 
England     and      on    the 
Continent,  and  by  Hunt, 
Allen,  and  others  in  the 
United    States;     for,    in 
leaving  out  some    parts 
of  Dr.  Gorrie's  machine, 
the  principles  of  all  the 
later    machines     are 
covered. 

A  reference  to  our 
illustration  will  show  the 
details  of  construction  of  the  compressed-air  freezing  apparatus 
of  Dr.  Gorrie ;  the  power  for  running  the  machine  not  being 
shown.  A  charging  tank,  containing  fresh  water  for  supplying 
the  freezing  can,  is  placed  overhead.  The  other  lettering  in- 
dicates details  readily  understood  by  inspection. 


Fig.  531.— side  elevation,  ice  machine. 

A,  The  air-compressing  cylinder  ;  By  receiver  or 
compressed-air  tank;  R,  cooling  tank  with  air-pipe 
coil  P;  />,  injection  pump  for  compressor  spray,  oper- 
ated by  cam  and  bell  crank  ;  C,  the  expansion  cylin- 
der ;  E,  expansion  cylinder  injection  pump,  not  shown, 
drawing  brine  from  the  jacket  //'and  forcing  it  in  a 
spray  into  the  expansion  cylinder,  by  which  the  brine 
is  quickly  cooled  and  discharged  with  the  cold  air  into 
the  upper  section  of  the  brine  jacket  and  tank  ;  _/,  the 
freezing  can  or  tank,  shown  in  Fig.  530,  above  the  in- 
sulated cvlinder. 


COMPRESSED-AIR    REFRIGERATING    MACHINE   AS  MADE   BY 
J.    AND    E.    HALL,    DARTFORD,    ENGLAND. 

The  machine  consists  of  three  cylinders,  fitted  with  metallic 
pistons  placed  side  by  side,  and  connected  by  a  crank  shaft, 
common  to  all,  by  means  of  piston  rods,  crossheads  with  slipper 


756 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


guides,  and  connecting  rods,  in  the  manner  common  with  ordi- 
nary horizontal  engines.  The  same  crank  shaft  drives  a  water- 
circulating  pump,  and  beneath  the  frame  which  carries  the 
whole  mechanism  is  a  tubular  refrigerator.  The  lower  cylinder 
in  Fig.  532  is  of  the  kind  ordinarily  made  for  steam  engines, 
and  may  be  constructed  with  expansion  valves,  steam  jacket, 
and  all  other  accessories  suitable  for  a  steam  engine  of  the  best 
construction. 

The  power  developed  in  this  cylinder  is  transmitted  through 
to  the  crank  shaft,  by  an  overhung  crank,  to  a  centre  crank, 
which  actuates  the  piston  of  the  middle  or  air-compressing  cyl- 
inder, which  is  water-jacketed,  and  fitted  with  double  slide 
valves,  through  which  air  is  drawn  in  from  the  outside  atmos- 
phere and  delivered,  compressed  to  about  45  pounds  per  square 
inch,  and  at  a  temperature  of  about  250°,  to  the  tubular  refrig- 
erator. The  hot  air  circulates  through  a  number  of  metal 
tubes,  round   the  outsides  of  which   passes  a  current  of  water 


Circulating  Pump 


Fig.  532.— plan,  hall  air-refrigehating  machlne. 


supplied  by  the  circulating  pump,  actuated  by  the  crank  shaft. 
The  water  rises  about  10°  in  temperature,  and  carries  off,  in  the 
form  of  heat,  a  portion  of  the  energy  of  the  steam  engine.  The 
compressed  air,  reduced  to  nearly  the  normal  temperature  and 
at  a  pressure  of  45  pounds  per  square  inch,  next  enters  the 
upper  cylinder  on  the  diagram,  through  double  slide  valves, 
and  is  made  to  expand,  doing  work  upon  the  piston,  and  there- 


REFRIGERATION. 


757 


fore  its  temperature  falls  in  proportion  to  the  amount  of  energy 
communicated  to  the  crank  shaft,  which  energy  is  applied  to 
reduce  the  work  to  be  done  by  the  steam.  The  temperature 
of  the  air  is  reduced  by  this  means  to  as  much  as  130°  below  the 
freezing-point.  In  some  cases,  instead  of  drawing  air  into  the 
compression  cylinder  from  the  atmosphere,  it  is  drawn   from 


Fig.  533.— section,  hall  air-refrigerating  machine. 


the  refrigerated  chambers,  and  is  made  to  pass  over  a  number  of 
tubes  containing  the  compressed  air,  which  is  thus  cooled  to  a 
still  lower  temperature  than  was  effected  by  the  cooling  water, 
the  result  being  that  a  relatively  lower  temperature  is  obtained 
after  expansion.  Simple  as  the  process  appears  to  be,  yet,  to 
obtain  the  best  results,  great  nicety  is  required  in  the  propor- 
tions of  the  cylinders,  in  the  extent  to  which  the  air  is  com- 
pressed, the  degree  to  which  the  air  is  expanded,  and  in  the 
practical  details  of  the  valve  gear,  which  are  especiall}^  impor- 
tant with  respect  to  the  difficulties  attendant  upon  the  forma- 
tion of  snow  and  ice  derived  from  the  freezing  of  the  moisture 
always  contained  in  the  air.  It  is  the  successful  treatment  of 
these  details  which  makes  the  difference  between  an  economi- 
cal and  trustworthy  machine  and  a  wasteful  or  uncertain  one. 
When  applied  to  refrigerate  the  holds  of  vessels  engaged  in  the 
dead-meat  trade,  the  money  value  depending  on  the  efficiency 
and  trustworthiness  of  a  machine  is  very  large. 


758  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

Setting  aside  friction,  the  power  necessary  to  drive  the  cir- 
culating pump,  and  the  heat  represented  by  radiation  and  con- 
duction, the  useful  work  done  by  the  steam  is  measured  by  the 
quantity  of  heat  carried  off  by  the  water  circulating  round  the 
cooling  tubes  and  the  compression  cylinder.  The  theoretical 
amount  of  cooling  is  easily  determined. 

The  air  under  an  absolute  pressure  of  four  atmospheres,  and 
at  a  temperature  a  little  above  that  of  the  surrounding  atmos- 
phere, say  at  60°,  is  expanded  along  the  adiabatic  curve  to  one 
atmosphere;  the  absolute  temperature  at  the  end  of  the  opera- 
tion will  therefore  be  theoretically — 
520° 


l—\  0.29  =  348°  absolute. 


which  is  144°  below  the  freezing-point,  instead  of  the  130°  at- 
tained in  practice.  The  air  in  expanding  absorbs  a  certain 
amount  of  heat  from  the  cylinder,  and  hence  the  slight  dis- 
crepancy. 

In  these  machines  about  50  per  cent  of  the  work  of  the 
compression  piston  is  returned  by  the  expansion  piston  as 
claimed  when  operated  on  cold  air  drawn  from  the  refrigerat- 
ing room. 

THE   ALLEN    DENSE-AIR    ICE    MACHINE. 

The  distinguishing  feature  of  the  Allen  dense-air  ice 
machine  (the  invention  of  Mr.  Leicester  Allen,  of  New  York) 
is,  that  it  takes  for  compression  not  air  of  atmospheric  pressure 
from  the  open  atmosphere  or  from  cooled  chambers  not  air 
tight,  but  air  of  considerable  pressure  which  is  contained  in  the 
machine  and  in  a  system  of  pipes. 

This  air  under  pressure  (generally  60  or  70  pounds)  is  taken 
in  by  an  air  compressor  and  compressed  to  commonly  210  or 
240  pounds.  This  heats  up  the  air,  storing  in  it  such  amount 
of  heat  as  is  the  equivalent  for  the  work  expended  upon  the 
compression.     It  is  then  passed  through  a  copper-pipe  coil  im- 


REFRIGERATION. 


759 


mersed  in  circulating  water,  which  removes  the  heat  to  nearly 
the  temperature  of  the  water. 

Then  the  air  passes  into  the  valve  chest  of  the  expander, 
which  is,  in  construction,  a  usual  steam  engine  with  a  cut-off 
valve.  The  valves  admit  the  highly  compressed  air  upon  the 
piston  to  a  certain  point  of  the  stroke  and  then  shut  it  off.  The 
piston  continues  to  travel  to  the  end  of  the  stroke,  the  air  ex- 
erting pressure  upon  it  (constantly  diminishing).     This  takes 


Fig.  534.— air  compressor  and  expandkr. 
Horizontal  type  of  the  Allen  system.    H.  B.  Roelker,  41  Maiden  Lane,  N.  Y.  City. 

out  of  the  air  such  a  quantity  of  heat  as  the  work  performed  by 
the  air,  while  expanding,  requires  for  its  performance. 

The  result  is  a  very  low  temperature  of  the  air  at  the  end  of 
the  stroke.  The  return  stroke  of  the  piston  pushes  it  C)ut 
through  thickly  insulated  pipes  to  such  places  as  are  to  be  re- 
frigerated, viz.,  the  ice-making  box,  the  meat  chamber,  and 
the  drinking-water  butt.  In  all  these  the  air  is  tightly  enclosed 
in  pipes  or  other  strong  apparatus,  being  under  the  original 
pressure  at  which  it  entered  the  compressor  (60  or  70  pounds), 
when  the  cold  is  given  out  through  the  metallic  surfaces. 

The  machine  usually  consists  of  the  following  parts,  refer- 
ring to  Fig.  536: 


76o 


COMPRESSKD    AIR    AM)    ITS    APPLICATIONS. 


A.  I'he  steam  engine,  which  is  of  usual  construction,  and 
to  its  crank  shaft  the  air  compressor  and  the  expander  are 
linked.  The  expander  helps  the  steam  cylinder  and  the  air 
compressor  takes  the  power. 

J>.  The   compressing    cylinder,    which   is   constructed   with 


i'^IG.   535.— AIR  COMPRESSOR   AND  EXPANDER. 
Vertical  tj-pe  of  the  Allen  system. 


slide  valves  instead  of  the  usual  conical  lift  valves,  in  order  to 
move  more  quickly  and  noiselessly. 

C.  The  copper  coil  placed  inside  of  a  cylinder  containing 
circulating  water.  In  this  the  highly  compressed  air  is  cooled 
to  nearly  the  temperature  of  the  water. 


REFRIGERATION. 


761 


D.  The  expander  cylinder,  which  is  constructed  like  a  usual 
steam-engine  cylinder,  with  slide  valve  and  cut-off  valve.  It 
must  cut  off  the  pressure  at  such  a  point  that  the  expanded  air 
at  the  end  of  the  stroke  of  the  piston  is  very  nearly  of  the  same 
pressure  as  the  air  contained  in  the  system  of  pipes.  If  it  were 
of  much  higher  pressure  it  would,  at  exhausting,  warm  up 
again,  by  exerting  its  remaining  power  in  producing  velocities 
and  frictions  inside  of  the  apparatus. 

E  is  2i  trap  which  gathers  out  of  the  cold  air  the  lubricat- 


FlG.    536.  -CYCLE   OF   COMPKESSED-AIR    KEFRIGERATIOX. 

ing  oil  which  is  used  in  the  compressor  and  expander  cylinders; 
also  some  snow.  It  contains  a  jacket  connectable  to  steam,  in 
order  to  liquefy  the  frozen  contents  when  they  are  to  be  blown 
out. 

F  is  the  water  pump  which  circulates  water  around  the 
copper  coil  C,  and  through  a  water  jacket  which  surrounds  the 
working  cylinder  of  the  air  compressor  B,  in  order  to  prevent 
the  heat  from  injuring  the  packings. 

6^  is  a  small  air-compressing  pump  which  takes  air  from 


762  COMPRESSED   AIR   AND    ITS    APPLICATIONS. 

the  atmosphere  and  pushes  it  into  the  machine  and  pipe  sys- 
tem. This  charges  the  system  with  the  requisite  air  pressure 
when  the  machine  starts  to  work,  and  maintains  the  pressure 
against  leakages  occurring  at  the  stuffing-boxes  and  joints. 
This  air  contains  the  usual  atmospheric  moisture;  and  to  expel 
this,  the  outlet  pipe  from  this  pump  passes  the  air  through  the 
trap  //,  where  it  is  cooled  by  being  forced  into  very  close  con- 
tact with  the  cold  head  of  the  reservoir  for  coil  C.  This  cooling 
tinder  pressure  and  contact  with  moist  surfaces  deposits  out  of 
the  air  about  80  or  85  per  cent  of  the  contained  moisture, 
which  is  then  drained  off  by  pet-cocks,  leaving  pure  air  for  the 
refrigerating  work.  This  is  of  great  importance,  as  the  large 
amounts  of  latent  heat  in  the  water  vapor  and  of  latent  cold  in 
frozen  water  would  produce  very  serious  losses  in  the  result  of 
the  machine  if  the  air  contained  water,  which  would  be  subject 
to  the  heating  and  freezing  processes  which  occur  in  the  ma- 
chine.    Surplus  air  is  blown  off  by  a  small  safety  valve. 

The  air  pistons  are  packed  with  leather  soaked  in  castor  oil. 

The  air  stuffing-boxes  contain,  first,  a  few  rings  of  Katzen- 
stein  soft  metal  packing  rings,  then  a  hollow  oiling  ring,  then 
outer  layers  of  fibrous  packing,  usually  square  Garlock  packing. 
The  oiling  ring  is  kept  full  of  oil  by  a  sight-feed  pressure  lubri- 
cator which  is  connected  by  a  pipe  to  the  stuffing-box. 

The  air  pushed  out  by  the  expander  is  practically  of  about 
—  35°  to  —55°  F.,  depending  upon  the  temperature  of  the  cool- 
ing water  and  upon  internal  leaks  and  frictions.  The  pipes 
lead  it  first  through  oil  trap  E,  for  purification,  then  to  the 
ice-making  box  /,  which  consists  of  a  casting,  forming  pockets 
T,  for  the  reception  of  sheet-iron  ice  cans.  This  casting  is  set 
in  a  strong  and  tight-jacket  casting  with  internal  bulkheads, 
formed  so  that  the  cold  air  which  is  led  into  the  space  between 
jacket  and  ice-can  pockets  must  pass  closely  along  the  surfaces 
of  the  pockets. 

The  small  space  between  the  sheet-iron  ice  cans  and  the 
inside   of  the   pockets  is  filled  with  a  solution  of  about  equal 


REFRIGERATION.  763 

weights  of  chloride  of  calcium  and  water,  which  withstands  the 
cold  without  freezing.  It  provides  a  good  conductor  for  the 
cold  and  keeps  the  cans  from  freezing  fast  in  the  pockets. 

For  larger  apparatus,  a  wrought-iron  tank,  filled  with  re- 
frigerating pipes,  and  ice  cans,  all  immersed  in  the  above  brine, 
are  used. 

From  the  ice-making  box  the  cold  air  is  led  to  the  meat 
chamber  K,  where  it  is  passed  through  a  system  of  refrigerating 
pipes  L. 

Frozen  meat  can  be  kept  practically  without  change  for  an 
almost  indefinite  time.  When  kept  at  nearly  the  freezing-point 
without  change  it  will  remain  for  a  number  of  weeks  in  good 
condition.  A  good  practical  rule  for  the  amount  of  refrigerat- 
ing pipes  required  in  the  meat  chamber  to  keep  this  at  the 
freezing-point  is :  One  square  foot  of  pipe  surface  for  every 
2\  to  2f  square  feet  of  interior  surface  of  well-insulated  meat 
chamber,  omitting  interior  divisions.  It  is  necessary  to  arrange 
the  pipes  so  that  the  air  in  them  is  compelled  to  pass  all  sur- 
faces with  fair  velocity. 

From  the  meat  chamber  the  cold  air  goes  to  the  refrigerat- 
ing pipes  in  the  drinking-water  butt  M,  passing  first  to  the 
bottom  layer  and  then  gradually  upward. 

After  that  it  returns  to  the  compressor  inlet  of  the  ma- 
chine. 

In  arrangements  where  all  the  cold  is  not  taken  out  of  the 
air  by  the  refrigerator  apparatus,  the  highly  compressed  air 
after  cooling  in  the  copper  coil  is  further  cooled  in  a  special 
apparatus,  where  it  is  brought  into  surface  contact  with  the  re- 
turning and  still  cold  air,  before  entering  the  expander. 

Temperatures  of  70°  to  90°  below  zero  are  thus  practically 
obtained  in  these  machines. 

It  is  of  the  greatest  importance  that  all  apparatus  containing 
artificially  cooled  air  or  brine  should  be  very  heavily  insulated 
with  air-tight  and  waterproof  material,  because  the  water  vapor 
of  the  atmosphere  is  attracted  with  great  force  to  all  cold  sur- 


764  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

faces,  destroying  fibrous  materials  as  soaking  them  in  water 
would  do,  and  consuming  much  cold  b\  its  latent  heat. 

The  vertical  machines  have  the  same  parts  as  the  horizontal 
machines,  only  of  different  dimensions  and  different  detail  of 
position. 

COLD    STORAGE    AND    COLD    ROOMS  FROM  THE  DIRECT  EXPANSION 
OF    COMPRESSED    AIR. 

In  view  of  the  largely  increasing  demand  for  the  means  of 
preserving  food  in  the  warmer  sections  of  the  United  States, 
and  in  tropical  climates,  where  ice  cannot  be  obtained  or  the 
cost  is  so  great  as  to  preclude  its  use,  the  expansion  of  com- 
pressed air  as  a  constant  cooling  medium  is  one  of  the  means  at 
the  command  and  control  of  every  one  who  is  able  to  place  a 
small  outlay  for  a  valuable  boon  to  household  comfort;  and 
for  the  profit  that  may  be  realized  from  the  power  to  preserve 
fruit,  vegetables,  and  meat  for  sale,  or  for  the  time  and  oppor- 
tunity for  shipment  to  a  market. 

There  are  large  tracts  of  country  in  the  southern  section  of 
the  United  States  in  which  are  situated  plantations  and  farms, 
the  owners  and  managers  of  which,  having  the  financial  means 
to  supply  comforts  to  life  by  the  use  of  cold  preserved  food, 
yet  are  entirely  beyond  the  reach  of  ice,  either  natural  or  arti- 
ficial; with  them,  such  wants  may  be  supplied  by  means  of  any 
small  power,  such  as  a  windmill,  a  waterfall,  a  gasoline  or  oil 
engine,  operating  a  pump  for  the  compression  of  air.  In  Mexico 
and  the  Central  American  and  South  American  States,  the 
field  for  useful  work  by  wind  and  water  power  alone  for  con- 
tributing to  domestic  comfort  by  the  preservation  of  food  is  im- 
mense; where  power  from  nature  as  through  a  windmill  or 
water  wheel  can  be  utilized.  The  distance  need  not  be  consid- 
ered beyond  the  cost  of  a  small  pipe  for  conveying  the  com- 
pressed air,  as  a  considerable  length  is  needed  to  cool  the  air 
to  its  normal  temperature  when  it  has  been  heated  by  the  opera- 
tion of  compression ;  when  by  expansion  to  atmospheric  press- 


REFRIGERATION. 


765 


lire  an  approximate  amount  of  heat  may  be  eliminated  from 
the  expanding  air  as  was  accumulated  by  its  compression,  and 
from  which  a  large  cooling  efficiency  may  be  obtained. 


Compression  Volume 


Fig.  537.— theoretical  diagram  of  isothermal  air  compression  and  adiabatic  expan- 
sion FROM  various  PRESSURES  AND  NORMAL  TEMPERATURE  OF  60°  F. 


The  graphic  diagram  (Fig.  537)  has  been  made  to  show  at 
sight  the  theoretical  cooling  effect  produced  by  the  free  expan- 
sion of  dry  air  from  various  pressures  and  from  the  normal 


766  COMPRESSED    AIR   AND    ITS   APPLICATIONS. 

temperature  of  60°  F.  The  conditions  of  air  expansion  for  any- 
natural  temperature  of  the  stored  air  may  be  found  by  simply 
subtracting  the  difference  from  the  expansion  column  when  nor- 
mally above  60°,  or  adding  when  below  60°.  Thus,  in  an  at- 
mospheric temperature  of  80°,  the  cold  produced  by  expanding 
from  20  pounds  pressure  would  be  — 67°  instead  of  —87°,  as 
shown  in  the  diagram.  From  50  pounds  pressure  and  90°  at- 
mospheric temperature,  the  cold  air  of  expansion  would  be 
—  108°  instead  of  —138°,  as  in  the  diagram;  thus  for  any  at- 
mospheric condition  of  temperature  and  pressure,  the  theoreti- 
cal condition  of  cold  by  expansion  may  be  known  by  simple 
inspection  of  their  several  relations  as  shown  in  the  diagram. 

The  diagram  shows  much  that  is  interesting  in  regard  to 
the  general  conditions  and  effect  of  air  compression  and  expan- 
sion. It  will  be  seen  that  the  column  of  pressures  on  the  right 
corresponds  with  the  column  of  heat  developed  by  compression 
on  the  left,  while  the  upper  or  adiabatic  curve  shows  the  condi- 
tion of  temperature,  pressure,  and  volume  at  the  moment  of 
compression.  The  lower  or  isothermal  line  shows  the  shrink- 
age of  the  volume  due  to  the  cooling  of  air  to  its  normal  tem- 
perature. 

The  vertical  dotted  lines  from  the  intersection  of  the  iso- 
thermal line  with  the  horizontal  lines  of  pressure,  meeting  the 
atmospheric  line  from  the  starting-points  for  the  curves  of  ex- 
pansion, are  extended  on  the  same  scale  of  temperature  corre- 
sponding with  the  scale  of  compression. 

The  intersections  of  the  dotted  lines  extended  through  the 
curved  lines  of  expansion  show  also  in  a  graphic  way  the  frac- 
tional expansions  from  one  stage  of  compression  to  another 
lower  one,  as  measured  by  the  expansion  scale  at  the  left-hand 
side.  Thus  when  a  volume  of  air  at  60  pounds  pressure  and  60° 
temperature  is  expanded  to  30  pounds  pressure,  its  temperature 
will  fall  to  the  intersection  of  the  extended  dotted  line  of  30 
pounds  pressure  with  the  60-pound  curve,  which  measured  on 
the  expansion  scale  is  —57°;  and  so  on  for  any  other  pressures. 


REFRIGERATION.  J^y 

In  applying  the  conditions  of  air  expansion  to  the  practical 
effects  of  refrigeration  or  the  cooling  of  rooms  for  cold  storage 
and  preservation  of  food,  a  large  deduction  from  the  theoretical 
figures  for  the  degree  of  cold  by  air  expansion  must  be  made 
for  success. 

The  absorption  of  heat  from  the  walls  of  a  cold  room,  the 
cooling  of  a  large  body  of  air  in  the  room  and  of  food  products 
stored,  and  the  greater  loss  from  frequent  opening  of  a  cold 
room  for  the  removal  and  refilling,  with  the  natural  leakage  of 
cold  air  around  the  doors,  make  the  margin  of  loss  in  cold-air 
production  a  larger  one  than  at  first  appears  when  brought  into 
actual  use. 

The  amount  of  heat  contained  in  a  given  volume  of  air  is 
about  -gx4T  °^  ^^®  amount  contained  in  the  same  volume  of  wa- 
ter from  any  number  of  degrees  change  of  temperature  at  ordi- 
nary climatic  temperatures ;  so  that  there  is  a  large  margin  be- 
tween the  volume  of  cold  air  required  to  cool  a  room  filled  with 
air  only  and  the  volume  required  to  cool  a  room  filled  with  fruit, 
vegetables,  milk,  butter,  or  meat  containing  from  50  to  90  per 
cent  of  water,  and  of  which  the  solid  parts  also  have  a  far 
higher  specific  heat  than  air. 

This  property  of  water-loaded  food  accounts  for  the  time  re- 
quired to  cool  a  loaded  cold-storage  room  over  the  time  required 
for  cooling  an  empty  one,  as  well  as  the  necessity  for  so  pack- 
ing the  material  of  storage  that  the  cold  air  can  circulate  freely 
and  bring  every  part  to  the  required  temperature  in  the  short- 
est possible  time. 

As  to  the  work  that  compressed  air  will  do  in  cooling  rooms, 
there  is  a  large  marginal  range  in  the  quantity  of  free  air  re- 
quired for  a  specific  temperature,  due  to  the  conditions  of  tem- 
perature of  the  material  to  be  cooled  and  the  amount  of  com- 
pression in  the  air  to  be  expanded  for  this  duty,  less  the  work 
duty  of  expansion  and  the  losses  by  radiation  and  leakage. 

Assuming,  for  example,  a  cold  room  for  a  farm  or  plantation, 
of  1,000  cubic  feet  capacity,  or  say  12  feet  square  b)"  7  feet  high, 


768  COMPRESSED   AIR   AND    ITS   APPLICATIONS. 

thoroughly  insulated,  with  a  double  door  at  side  for  storing;  a 
single  or  trap  door  with  a  small  ventilator  at  top,  with  steps 
from  the  trap  door  for  every-day  use,  and  also  lighted  from  the 
top  (by  this  means  a  loss  of  cold  air  is  prevented  by  its 
greater  specific  gravity  holding  it  at  the  bottom).  The  room 
may  be  kept  uniformly  at  36°  F.  in  an  outside  temperature 
averaging  80°.  To  cool  such  a  room  without  storage  material, 
from  80°  to  36°  requires  a  loss  of  46°  in  a  volume  of  1,000  cubic 
feet  of  air,  say  ']']  pounds,  the  specific  heat  of  which  is  0.2375 
water  =  i.  Then  'jj  X  0.2375  =  18.2  heat  units  must  be  ab- 
sorbed for  every  degree  of  change  in  temperature.  Then  18.2 
X  44°  =  800  heat  units  must  be  abstracted  to  bring  it  to  36° 
F.,  leaving  out  the  cooling  of  the  walls,  displaced  air,  and  leak- 
age, which  will  be  only  a  matter  of  time  in  the  initial  operation. 
Assuming  to  use  an  air  pressure  of  only  30  pounds  per 
square  inch,  then  in  the  graphic  diagram,  tracing  the  dotted 
line  from  the  isothermal  curve  junction  of  30  pounds  and  fol- 
lowing its  curve  of  expansion,  we  have  —  13S  +  60°  to  the  at- 
mospheric temperature  =  198°  difference  in  temperature  to  be 
overcome  by  expansion  from   30  pounds  pressure,  or   198  heat 

units  per  pound  of  air.     Then =   '^'  '^  ,    or    17  pounds    X 

198       .2375 

13. 1  =  223  cubic  feet  of  free  air  at  30  pounds  pressure  will  be 
required  to  cool  the  room  to  36°. 

A  compressor  of  5  cubic  feet  per  minute  capacity,  using  less 
than  I  horse  power,  will  furnish  enough  air  to  reduce  the  tem- 
perature of  the  room  from  80°  to  36°,  in  which  the  displacement 
of  air  in  the  room  by  the  addition  of  223  cubic  feet  of  cold  air 
should  nearly  neutralize  the  loss  of  effect  by  resistance  and  ra- 

diation,  when  the  theoretical  time  -^^  =  45    minutes  may  be 

doubled  to  about  i^  hours,  and  should  then  easily  furnish  cold 
air  for  absorption  of  heat  from  the  material  of  storage  and  to 
supply  the  waste  made  necessary  by  ventilation  and  radiation 
with  a  constant  work  of  less  than  a  half  horse  power.     This 


REFRIGERATION.  769 

power  comes  within  the  scope  of  a  cheap  class  of  water  wheels, 
water  motors,  and  the  smaller  sizes  of  gasoline  and  oil  engines 
and  windmills. 

Where  intermittent  power  must  be  used,  as  with  windmills 
and  power  engines,  a  system  of  storage  of  compressed  air  may- 
be used  with  perfect  satisfaction  as  affording  a  constant  flow  of 
air  into  the  cold  room  and  also  into  a  small  refrigerator,  which 
will  be  found  a  most  useful  adjunct  for  household  use  for  cool- 
ing drinking-water. 

The  amount  of  pipe  surface  required  for  cooling  compressed 
air  to  the  normal  temperature  is  a  matter  of  much  importance, 
as  its  delivery  at  the  point  of  expansion,  to  be  effective,  must 
be  at,  or  very  near,  the  temperature  of  the  outside  atmosphere. 

The  method  of  keeping  the  air-cooling  pipe  at  the  proper 
temperature  fixes  the  amount  of  pipe  surface  to  be  provided. 

For  30  pounds  pressure,  1 5  square  feet  of  cooling  surface 
per  cubic  foot  of  free  air  used  per  minute  is  a  fair  proportion 
for  an  air-cooling  coil  exposed  to  a  free  circulation  of  the  at- 
mosphere and  shaded  from  the  sun's  heat. 

This  would  indicate  a  coil  of  150  feet  of  i^-inch  pipe  for  the 
requirement  of  a  cold  room  as  above  stated,  which  may  also  in- 
clude the  leading  pipe  from  compressor  to  cold  room,  if  favor- 
ably situated  for  cooling.  Where  it  is  convenient  to  use  water 
for  cooling,  either  by  a  sprinkler  or  by  submerging  the  coil  in  a 
tank  of  water  fed  from  a  stream  or  by  pumping,  the  size  of  the 
coil  may  be  greatly  reduced,  according  to  the  temperature  of 
the  water. 

For  an  intermittent  power  as  a  windmill,  or  a  gasoline  en- 
gine that  would  not  be  convenient  to  run  at  night,  a  storage  of 
air  will  be  necessary  by  the  use  of  a  proportionally  increased 
power  during  the  day  for  accumulating  compressed  air  in  tanks. 
For  night  cooling,  after  the  room  has  once  been  brought  down 
to  the  required  temperature,  the  quantity  of  air  per  hour  will  be 
much  lessened,  so  that  the  estimated  storage  of  sufficient  air 

for  a  ten-hours'  run  of  the  above  plant  will  require  tanks  to 
49 


770  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

hold  about  1,200  cubic  feet,  or  say  3  tanks  of  cylindrical  form 
5  feet  diameter,  2  i  feet  long.  As  the  atmospheric  temperature 
always  falls  at  night  in  tropical  and  semi-tropical  regions,  the 
conditions  of  compressed-air  supply  may  be  much  modified  in 
the  storage  quantity  above  outlined  by  partially  closing  the  air- 
inlet  valve:  and  where  constant  power  can  be  obtained,  the 
whole  question  of  cold  storage  for  private  use  becomes  a  cheap 
and  simple  one. 

The  arrangement  of  the  nozzle  or  orifice  for  delivering  the 
compressed  air,  and  at  which  point  the  expansion  takes  place, 
is  important,  and  requires  its  area  to  be  exactl}'  gauged  to  the 
proper  size  for  the  delivery  of  the  desired  volume  of  air  at  the 
assigned  pressure.  At  30  pounds  pressure,  air  flows  through 
an  orifice  in  a  thin  plate  at  the  rate  of  525  feet  per  second. 
Then  for  the  plant  as  above  described,  for  the  issuance  of  5  cu- 
bic feet  of  free  air  per  minute  under  a  compression  of  3  volumes 

in   I,  is ^ =  0.02777  cubic  feet  of  compressed  air  per  sec- 

3  X  60 

ond,    and         ''         =  0.0000529   of    a   square-foot    area.     Then 

525 
0.0000529  X  144  =  0.0076176  of  a  square  inch.  Then  enlarg- 
ing for  the  coefficient  of  efflux,  the  orifice  should  be  i-inch  di- 
ameter, with  a  needle  valve  in  it  to  adjust  or  to  shut  off  the  air 
flow  when  required.  Means  should  also  be  provided  for  blow- 
ing off  any  water  that  may  condense  in  the  air  pipes  or  storage 
tanks  by  the  cooling  of  the  air  after  compression. 

With  proper  care  and  a  moderate  outlay  the  system  of  cold 
storage  by  compressed  air  becomes  a  simple,  efficient,  and  eco- 
nomical adjunct  to  the  living  comforts  of  every  home  in  a 
warm  climate  not  blessed  with  a  nearby  ice-making  plant. 


COOL    WATER    FOR    DRINKING    IN    THE    MACHINE    SHOP. 

Mr.  Frank  Richards  in  The  American  Machinist  has  made  the 
following  suggestion  for  obtaining  this  desirable  comfort,  in 
shops  using  compressed  air: 


REFRIGERATION.  77 1 

"  A  vertical  cylindrical  reservoir  should  be  provided  and 
connected  to  the  water  supply.  This  reservoir  would  be  con- 
stantly full  of  water,  and  while  contained  therein  the  cooling  of 
the  water  would  take  place.  The  water  should  enter  the  reser- 
voir at  the  top,  and  be  drawn  off  at  the  bottom,  and  the  draught 
pipe  after  leaving  the  reservoir  should  be  as  short  as  possible, 
so  that  the  water  after  being  cooled  may  not  have  a  chance  to 
warm  up  again.  The  cooling  of  the  water  would  be  accom- 
plished by  the  passage  of  expanded  air  through  a  coil  of  pipe 
closely  surrounding  the  reservoir,  the  air  entering  at  the  bottom 
of  the  coil,  and  escaping  at  the  top.  The  air  should  be  brought 
to  the  cock  which  controls  the  admission  to  the  coil  at  full  press- 
ure, say,  70  to  So  pounds  gauge,  and  at  the  temperature  of  the 
surrounding  air.  The  compressed  air,  while  under  full  press- 
ure and  before  reaching  this  point,  should  have  been  allowed 
to  deposit  all  the  moisture  it  could  get  rid  of  by  passing  through 
a  suitable  chamber  or  air  receiver  after  being  thoroughl}' 
cooled.  A  receiver  near  the  compressor,  and  through  which 
the  air  passes  before  it  is  entirely  cooled,  serves  to  equalize  the 
pressure  against  sudden  fluctuations,  but  it  does  not  get  rid  of 
the  moisture.  A  chamber  through  which  the  air  may  pass 
after  it  is  thoroughly  cooled  will  do  so.  As  the  air  comes  to 
the  coil  under  pressure,  and  at  normal  temperature,  upon  being 
released  from  pressure,  and  flowing  into  the  coil  at  atmospheric 
pressure,  and  expanded  to  four  or  five  times  its  previous  vol- 
ume, it  is  much  lowered  in  temperature,  and  immediately  be- 
gins to  draw  heat  from  the  walls  of  the  water  reservoir  which 
it  encircles,  thereby  cooling  the  water  contained  in  the  reser- 
voir. The  air  coil  instead  of  surrounding  the  water  reservoir 
may  be  entirely  within  it,  and  directly  in  contact  with  the  wa- 
ter. The  latter  is  the  better  arrangement,  but  in  either  case 
the  entire  air  coil  and  water  reservoir  must  be  enclosed  in  a 
thoroughly  effective  non-conducting  jacket  or  covering. 

"Now.  the  getting  of  this  coil  and  reservoir  and  all  that, 

too 

and  rigging  it  up  properly,  is  too  great  an  undertaking,  and 


'J']2  COMPRESSED    AIR    AM)    ITS    APPLICATIONS. 

one  that  few  will  be  likely  to  undertake  at  first,  so  we  have  to 
snggest  a  way  of  doing  it  all  with  such  material  as  is  generally 
available,  and  which,  because  we  have  it  handy,  we  generally 
assume  to  cost  nothing.  Take  a  i]-inch  pipe  loo  feet  long — 50 
feet  might  be  long  enough — place  it  horizontally,  and  connect 
one  end  of  it  to  the  compressed-air  supply  with  a  suitable  cock 
to  control  the  escape  of  the  air.  Leave  the  other  end  of  the 
pipe  open  and  enclose  the  whole  of  the  pipe,  after  passing  the 
air-admission  cock,  in  a  thick  non-conducting  covering.  If  you 
have  nothing  better  at  hand  take  plenty  of  paper,  v.-inding  it  on 
layer  after  layer  and  covering  the  whole  pipe.  Then  lead  a 
•f-inch  water  pipe  into  the  open  end  of  the  air  pipe,  and  let  it 
come  out  by  a  tee  or  otherwise  at  the  other  end  of  the  air  pipe, 
and  you  have  the  whole  apparatus.  The  air  in  this  case,  as  be- 
fore, should  be  brought  to  where  it  is  to  be  used  thoroughly 
cooled  and  with  all  its  water  discharged." 


Chapter  XXXIV. 


THE  HYGIENE  OF 
COMPRESSED    AIR 


THE    HYGIENE   OF    COMPRESSED    AIR. 

It  is  more  than  half  a  century  since  the  properties  of  com- 
pressed air  as  a  remedial  agent  were  put  forward  as  a  theory  and 
in  practice  in  "compressed-air  baths,"  and  claimed  to  be  espe- 
cially useful  in  the  treatment  of  pulmonary  diseases  and  of  dys- 
pepsia. As  the  pressure  employed  in  the  air  baths  was  com- 
paratively slight,  usually  from  8  to  lo  pounds  per  square  inch, 
the  effects  observed  differed  widely  from  those  produced  by  the 
high  pressure  employed  in  engineering  and  submarine  work. 
This  difference  is  not  only  in  degree  but  also  in  kind,  and 
therefore  the  literature  relating  to  compressed  air  as  a  remedy, 
although  extensive  and  interesting,  throws  no  light  upon  the 
effect  of  high  pressure  upon  the  human  system. 

It  is  only  in  the  actual  work  of  caisson  sinking  and  diving 
in  submarine  work  that  reliable  conditions  as  to  the  influence 
of  compressed  air  on  our  vital  condition  have  been  observed.  It 
is  noted  that  at  three  atmospheres  absolute,  30  pounds  gauge 
pressure,  it  is  impossible  to  whistle;  that  in  compressed  air 
at  considerable  tension,  every  one  speaks  through  his  nose; 
that  men  under  air  pressures  in  ascending  caisson  ladders  were 
much  less  out  of  breath  than  with  the  same  work  in  the  open 
air. 

In  speaking,  the  tongue  moves  stiffly  and  with  difficulty. 
Sounds  are  not  heard  with  their  usual  intensity.  The  secretion 
of  urine  is  decidedly  increased. 

The  most  usual  affection  is  muscular  pains,  occurring  either 
alone  or  ushering  in  other  symptoms.  When,  through  lack  of 
proper  ventilation,  the  caisson  air  becomes  impregnated  with 
the  smoke  of  lamps  and  carbonic-acid  gas  from  respiration,  all 
pathogenic  conditions  become  intensified. 


TJ^  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

Experience  has  taught  that  the  ill  effects  are  in  proportion 
to  the  rapidity  with  which  the  transition  is  made  from  the  com- 
pressed air  to  the  normal  atmosphere. 

Under  pressures  of  40  to  50  pounds  per  square  inch,  taste, 
smell,  and  the  sense  of  touch  lose  their  acuteness. 

During  the  time  pressure  is  increasing  the  hearing  is  affect- 
ed, with  a  feeling  of  increasing  warmth  in  the  skin,  as  if  going 
into  a  warm  room.  The  pulse  becomes  small  and  thready, 
sometimes  imperceptible,  ^"enous  blood  becomes  of  a  bright 
red  hue.  The  lungs  seem  to  increase  in  development,  while 
the  motion  of  the  ribs  is  reduced.  vShortness  of  breath  is  occa- 
sionally produced;  increase  of  appetite  is  experienced,  seldom 
thirst. 

While  the  pressure  remains  .stationary,  all  subjective  phe- 
nomena disappear,  to  return  again  during  locking  out  from  a 
caisson,  when  ringing  of  the  ears  and  bulging  of  the  ear-drums 
are  observed ;  taste  and  smell  return ;  a  prickling  sense  of 
warmth  is  felt  in  the  nostrils,  which  is  sometimes  followed  by 
bleeding  at  the  nose.  At  the  same  time  the  rapid  decline  of 
the  temperature  from  the  expansion  of  the  air  causes  extreme 
chilliness. 

On  going  out  from  a  caisson,  intense  pains  in  the  ears  and 
muscles  sometimes  occur,  which  are  much  modified  or  avoided 
by  a  slow  change  of  air  pressure. 

A  good  rule  has  been  established  to  allow  of  five  minutes 
for  locking  out  from  7  pounds  pressure ;  seven  minutes  from 
15  pounds;  ten  minutes  from  20  pounds;  twelve  minutes  from 
30  pounds,  and  so  on,  with  proper  increase  of  clothing  to 
counteract  the  chill  from  the  decreasing  pressure  in  the  air  lock. 

A  serious  inconvenience  is  experienced  by  workers  in  cais- 
sons, where  gas  or  lamps  are  used,  from  theunconsumed  carbon 
or  smoke  floating  in  the  dense  air.  Its  inhalation  produces 
more  or  less  irritation  of  the  air  passages  and  gives  rise  to  a 
very  characteristic  black  expectoration,  which  often  continues 
for  a  long  time  after  the  caisson  work  is  finished. 


THE    HYGIENE    OF    COMPRESSED    AIR.  'J'jy 

Comparative  immobility  of  compressed  air  from  its  density, 
which  retards  the  velocity  of  the  air  currents  necessary  to  per- 
fect combustion,  has  been  assigned  as  the  cause  of  smoky  lamps 
and  gas-jets  in  caisson  work.  A  watch  beats  slower  in  com- 
pressed air. 

The  following  abstract  from  the  prize  essay  of  Andrew  H. 
Smith,  M.D.,  on  the  effects  of  high  atmospheric  pressure  in 
caissons,  is  of  great  value  to  workers  in  compressed  air: 

EFFECTS    OF    COMPRESSED    AIR. 

The  effects  of  a  highly  condensed  atmosphere  upon  the 
system  may  be  divided  into  those  which  are  physiological  or 
consistent  with  health,  and  those  which  are  pathological  and 
constitute  or  induce  disease. 

The  physiological  effects  will  be  considered  according  to 
the  organs  or  functions  in  which  they  are  exhibited. 

Effect  on  the  Hearing:  It  is  a  law  of  acoustics  that  within 
the  limit  of  mobility  the  denser  the  medium  through  which  the 
sound  waves  are  communicated,  the  larger  the  wave,  and  there- 
fore the  louder  the  sound.  This  supposes,  of  course,  that  the 
ear  itself  remains  under  normal  conditions.  Such,  however,  is 
not  the  case  when  the  observer  is  in  a  highly  condensed  atmos- 
phere. The  unusual  pressure  upon  all  parts  of  the  auditory 
apparatus  opposes  a  mechanical  obstacle  to  the  freedom  of 
vibration,  which  is  essential  to  perfect  hearing.  Hence,  al- 
though larger  sound  waves  may  strike  upon  the  ear-drum, 
feebler  impressions  are  communicated  to  the  auditory  nerve, 
and  the  sound  appears  to  be  fainter  than  in  the  open  air.  Thus 
by  repeated  experiments,  I  found  that  a  watch  that  could  be 
heard  distinctly  at  a  distance  of  eighteen  inches  in  a  very  noisy 
place  in  the  open  air,  could  not  be  heard  at  a  greater  distance 
than  two  inches  in  the  comparative  silence  of  the  caisson. 

At  the  same  time  the  velocity  of  the  waves  of  sound  is 
greater,  and  hence  the  pitch  is  higher.     A  deep  bass  voice  is 


yj':>  COMPRESSED    AIR    AND    ITS   APPLICATIONS. 

changed  to  a  shrill  treble,  and  the  prolonged,  heavy  sound  of 
a  blast  is  so  modihed  as  to  resemble  the  sharp  report  of  a  pistol. 

This  modification  of  sound  is  very  striking,  and  is  almost 
the  only  thing  to  remind  the  casual  observer  that  he  is  moving 
about  in  an  atmosphere  three  or  four  times  as  dense  as  that  to 
which  he  is  accustomed. 

A  curious  fact,  noticeable  under  these  circumstances,  and  one 
which  was  long  ago  observed  in  diving-bells,  is  that  it  is  im- 
possible to  whistle.  The  utmost  efforts  of  the  expiratory  mus- 
cles is  not  sufficient  to  increase  materially  the  density  of  the 
air  in  the  cavity  of  the  mouth,  and  hence  on  its  escape  there  is 
not  sufficient  expansion  to  produce  a  musical  note.  A  similar 
difficulty,  though  in  a  less  degree,  is  experienced  in  speaking, 
and  for  this  reason  protracted  conversation  is  very  fatiguing. 

Effect  upon  Respiration :  In  a  highly  compressed  air,  the 
frequency  of  the  respiration  is  increased.  Dr.  Jaminet  gives 
the  rate  as  21  per  minute,  with  a  pressure  of  ^},  pounds,  which 
accords  with  my  own  observations.  He  ascribes  this  increase 
of  three  or  four  per  minute  to  an  increased  absorption  of  oxygen. 
Experiments  show,  however,  that  simply  increasing  the  supply 
of  oxygen  dhninishcs  the  frequency  of  respiration  instead  of  in- 
creasing it.  The  true  explanation,  I  think,  is  to  be  found  in 
the  fact  that  the  quantity  of  carbonic  acid  held  in  solution  by 
blood,  as  by  water,  is  in  proportion  to  the  pressure  to  which  the 
gas  is  subjected ;  and  hence  with  the  pressure  existing  in  the 
caisson,  the  elimination  of  carbonic  acid  from  the  blood  would 
not  be  as  perfect  as  under  normal  circumstances,  unless  the  air 
iu  the  lungs  were  more  frequently  changed.  As  ob.served  by 
Frangois  and  Dr.  Jaminet,  the  depth  of  the  inspirations  is  also 
increased. 

Effect  upon  the  Circulation :  It  has  been  shown  by  numer- 
ous observers  that  under  a  slightly  increased  pressure,  such  as 
is  employed  in  compressed-air  baths,  the  pulse  loses  in  fre- 
quency from  the  first.  This  is  doubtless  due  to  an  increased 
absorption  of  oxygen  by  the  blood,  which  thus  affords  a  suffi- 


THE    HYGIENE    OF    COMPRESSED    AIR.  779 

cient  supply  to  the  tissues  without  the  necessity  of  keeping  up 
the  usual  activity  of  the  circulation.  In  the  course  of  some 
experiments  undertaken  nearly  four  years  ago,  I  demonstrated 
that  the  same  effect  results  under  a  normal  pressure  from  add- 
ing oxygen  to  the  air  inhaled.  But  as  the  pressure  increases 
the  question  is  transferred  from  the  domain  of  chemistry  to 
that  of  mechanics.  The  condensation  of  the  tissues  from  the 
pressure  to  which  they  are  subjected,  and  the  consequent  nar- 
rowing of  the  vessels,  oppo.se  a  physical  obstacle  to  the  circula- 
tion, which  is  felt  before  the  blood  has  time  to  become  sur- 
charged with  oxygen,  and  while  there  is  still  a  necessity  for  an 
active  circulation.  The  labor  of  the  heart  is  thus  increased, 
and  its  action,  in  consequence,  excited.  I  have  frequentlv 
.seen  the  pulse  rise  to  120  immediately  upon  entering  the  cais- 
son, where  the  pressure  was  from  30  to  35  pounds  to  the  inch. 
But  after  the  lapse  of  a  period  varying  in  different  cases 
from  half  an  hour  to  two  hours,  the  pulse  falls  back  to  its  nor- 
mal standard,  or  even,  it  may  be,  below  it.  The  blood  has 
now  became  saturated  with  oxygen,  and  consequently  a  less 
active  circulation  is  demanded. 

Doubtless,  if  the  pressure  were  very  gradually  admitted, 
the  preliminary  rise  in  the  pulse  would  not  take  place,  the 
favorable  chemical  action  keeping  in  advance  of  and  counter- 
acting the  unfavorable  mechanical  conditions. 

The  effect  of  high  atmospheric  pressure  upon  the  volnjiie  of 
the  pulse  is  always,  according  to  my  observation,  to  diminish 
it.  This  is  easily  accounted  for  by  the  pressure  exerted  upon 
the  artery,  which  prevents  its  3aelding  readily  to  the  expanding 
force  of  each  successive  wave  of  blood.  Hence,  the  pulse  is 
small,  hard,  and  wiry.  These  characteristics  are  independent, 
in  a  great  degree,  of  the  frequency  of  the  beat,  although  as  the 
heart  recovers  from  the  irritable  condition  into  which  it  is 
thrown  by  the  sudden  increase  of  the  pressure,  and  settles 
down,  so  to  speak,  more  calmly  to  its  work,  it  contracts  with 
more  force,  and  the  pulse  gains  somewhat  in  volume. 


78o  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

It  is  remarkable  that  the  wide  variations  in  the  pulse-rate 
observed  were  not  accompanied  by  any  symptoms  appreciable 
to  the  individual.  A  man  with  a  pulse  of  fifty-two,  and  an- 
other with  one  of  one  hundred  and  sixteen,  felt  equally  well, 
and  each  was  entirely  unconscious  of  anything  imusual  in  the 
heart's  action. 

The  effect  of  the  pressure  upon  the  cutaneous  vessels  is 
shown  by  the  pallor  of  the  face,  which  is  very  marked,  and 
continues  for  fifteen  or  twenty  minutes  after  leaving  the  cais- 
son. The  hands,  too,  feel  shrunken,  and  the  palmar  surface 
of  the  fingers  is  often  shrivelled,  as  if  soaked  in  water.  The 
pressure  acting  upon  all  sides  of  the  fingers  empties  them  to  a 
considerable  extent  of  blood,  rendering  the  skin  apparently  too 
large  for  them.  The  veins,  too,  on  the  back  of  the  hand  .seem 
to  be  effaced. 

Effect  upon  Temperature:  In  none  of  the  reports  upon  the 
effects  of  high  pres.sure  as  employed  for  engineering  purposes, 
have  I  been  able  to  find  any  records  of  temperature.  J.  Lange, 
however,  found  that  under  the  comparatively  slight  pressure 
which  is  used  as  a  remedy,  the  temperature  of  the  body  suffered 
a  slight  decrease.  This  is,  no  doubt,  due  to  an  increased  ab- 
sorption of  oxygen,  which  has  been  shown  by  INIr.  Savory  and 
also  by  experiments  of  my  own  to  produce  this  effect. 

The  temperature  of  the  body  in  health  is  kept  at  about  98.6° 
F.,  by  the  constant  evaporation  from  the  surface.  But  in  the 
caisson,  as  already  mentioned,  the  air  was  always  nearly  or 
quite  saturated  with  moisture,  so  that  evaporation  from  the 
surface  must  have  been  practically  suspended.  With  the  tem- 
perature of  the  air  at  76°,  as  it  was  at  the  time  of  the  observa- 
tions, and  the  men  engaged  in  severe  labor,  it  is  easy  to  see 
how  the  absence  of  the  cooling  process  of  evaporation  from  the 
surface  would  lead  to  a  rise  of  one  degree  of  the  thermometer. 
This  view  is  strengthened  by  the  result  of  three  observations 
on  a  subsequent  occasion,  when  the  temperature  in  the  caisson 
stood  at  81°  in.stead  of  76°.     The  average  in  this  instance  was 


THE    HYGIENE   OF    COMPRESSED    AIR.  78 1 

101".  A  rise  of  five  degrees  in  the  temperature  of  the  air  could 
not  sensibly  affect  the  rapidity  of  tissue-change,  but,  if  not 
counteracted  by  evaporation  from  the  skin,  it  would  soon  tell 
upon  the  temperature  of  the  body. 

The  influence  of  the  hygrometric  condition  of  the  atmos- 
phere upon  the  temperature  of  the  body  is  a  matter  of  daily 
observation.  On  a  clear,  dry  day,  with  a  high  barometer,  we 
are  surprised  to  find  the  thermometer  indicating  a  temperature 
much  higher  than  our  sensations  would  lead  us  to  expect, 
while  on  the  contrary,  on  a  cloudy  day,  with  a  low  barometer, 
we  can  scarcely  persuade  ourselves  that  the  temperature  is  not 
many  degrees  higher  than  the  thermometer  indicates.  In  the 
dry,  clear  air  of  New  Mexico  I  have  supported  a  temperature 
of  1 10°,  without  inconvenience,  while  in  the  humid  atmosphere 
of  the  Florida  Keys  I  have  found  it  almost  unbearable  at  86°. 

Effect  upon  the  Perspiratory  Function  :  Several  writers  have 
observed  that  it  is  immediately  remarked  by  every  one  entering 
a  caisson  that  the  secretion  from  the  skin  is  apparently  im- 
mensely increased.  It  is  noticeable  even  when  the  temperature 
of  the  air  is  moderate,  but  as  this  increases  it  becomes  a  very 
serious  annoyance.  The  clothing  quickly  becomes  saturated, 
which,  besides  the  discomfort  it  occasions,  exposes  to  great 
danger  of  taking  cold  on  going  out  into  the  open  air. 

But  a  little  examination  served  to  show  that  in  the  New 
York  caisson,  at  least,  there  was  really  no  increase  of  the  secre- 
tion from  the  skin,  but  that,  instead  of  evaporating,  the  moist- 
ure accumulated  upon  the  surface,  and  thus  stimulated  excessive 
sweating.  This  was  owing  to  the  moist  condition  of  the  atmos- 
phere already  mentioned,  which  rendered  the  drying  of  the 
surface  by  evaporation  impossible.  The  atmosphere  possessed 
to  an  extreme  degree  the  quality  of  "mugginess,"  and  the  ap- 
parently profuse  perspiration  was  merely  an  exaggeration  of 
what  we  suffer  from  in  very  damp  weather,  even  though  the 
temperature  be  not  extreme. 

So  far   from  the  perspiratory  glands  being  stimulated   by 


782  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

the  density  of  the  atmosphere,  it  is  probable  that  the  anaemia 
of  the  skin  already  described,  as  resulting  from  the  pressure 
upon  the  surface,  would  tend  to  lessen  the  secretion  by  dimin- 
ishing the  supply  of  blood  to  the  glands. 

That  there  is  not  an  undue  amount  of  fluid  carried  off 
through  the  skin,  is  shown  by  the  absence  of  thirst  so  generally 
remarked. 

The  foregoing  explanation  of  the  apparent  increase  of  per- 
spiration is  important,  as  it  bears  upon  the  theory  of  excessive 
waste  of  tissue,  in  which  the  perspiration  is  supposed  to  aid. 

Effect  upon  Digestion  :  Nearly  all  authors  who  have  written 
upon  the  effects  of  compressed  air  agree  in  stating  that  for  a 
time,  at  least,  it  increases  the  appetite  to  a  remarkable  extent. 
Indeed  this  is  one  of  the  first  and  most  favorable  results  ob- 
served where  compressed  air  is  applied  remedially.  With  this 
experience  my  own  observations  in  the  main  agree.  It  was 
frequently  remarked  by  the  men  working  in  the  New  York 
caisson  that  their  work  made  them  unusually  hungry,  that  they 
"could  not  get  enough  to  eat,"  etc.  Of  course,  it  was  not  pos- 
sible to  obtain  any  exact  data  as  to  the  relative  amount  of  food 
con.sumed,  but  from  careful  inquiries  I  arrived  at  the  conclusion 
that  it  was  considerably  in  excess  of  what  is  usual  in  the  case 
of  men  engaged  in  similar  labor  in  the  open  air.  vStill,  there 
were  many  exceptions  to  the  general  rule,  especially  among 
those  who  had  been  long  engaged  upon  the  work,  and  whose 
general  tone  was  beginning  to  deteriorate.  Among  these,  loss 
of  appetite  was  often  complained  of. 

The  fact  of  this  generally  increased  appetite  seems  to  point 
to  an  increased  waste  of  tissue,  to  be  supplied  by  a  greater  con- 
sumption of  food.  An  increased  absorption  of  oxygen,  such  as 
we  assume  to  take  place,  seems  from  the  observations  of  several 
authorities  to  imply  greater  activity  of  tissue  change  as  the 
nltbnate  result.  But  in  this  case  I  think  it  is  scarcely  safe  to  ac- 
cept this  explanation  at  once  as  conclusive  and  sufficient.  It  may 
well  be  questioned  whether    during  the  actual  sojourn  in  the 


THE    HYGIENE    OF    COMPRESSED    AH-l.  783 

caisson  the  functions  of  digestion,  absorption,  and  assimilation 
proceed  normally  under  the  wide  departure  of  the  system  from  its 
natural  conditions.  If  it  could  be  shown  that  a  considerable  por- 
tion of  the  food  taken  before  entering  the  caisson  is  but  imper- 
fectly digested  or  assimilated,  the  subsequent  hunger  would  be 
readily  accounted  for.  I  am  not  aware  that  this  point  has  ever 
been  investigated,  but  I  can  scarcely  believe  that  such  an  in- 
crease of  appetite  as  is  described  could  depend  wholly  upon  in- 
creased interstitial  change  without  giving  rise  to  marked  eleva- 
tion of  tempeiature  and  other  symptoms  denoting  unusual 
chemical  activity. 

Effect  upon  the  Urinary  Secretion:  Dr.  Jaminet,  in  his  ob- 
servations at  St.  Louis,  found  that  the  amount  of  fluid  secreted 
by  the  kidneys  was  very  much  increased,  in  some  instances 
nearly  doubled,  while  the  specific  gravity  was  but  little,  if  at 
all,  below  the  usual  average.  This  shows  that  the  solid  matter 
excreted  was  also  in  much  greater  quantity  than  usual.  But  I 
cannot  agree  with  him  in  attributing  this  exclusively  to  the  ex- 
cessive waste  of  tissue  from  over-oxidation  of  the  blood.  The 
explanation  is  to  be  found,  I  think,  chiefly  in  the  fact  that  the 
skin,  as  already  stated,  performs  its  function  very  imperfectly, 
owing  to  the  impossibility  of  evaporation  from  the  surface  when 
the  air  is  already  loaded  with  moisture,  and  hence  a  portion  of 
its  duty  is  forced  upon  the  kidneys,  organs  always  ready  to  act 
vicariousl}'  for  the  skin  or  the  mucous  surfaces. 

Furthermore,  the  excretion  of  a  large  amount  of  urea  indi- 
cates a  relatively  deficient  oxidation  of  tissue,  and  is  one  of  the 
characteristics  of  those  diseases  in  which  respiration  is  suddenly 
embarrassed,  as,  for  instance,  pneumonia. 

Another  circumstance  not  to  be  lost  sight  of  is,  that  the 
pressure  upon  the  surface  acts  mechanically  to  congest  all  the 
abdominal  viscera,  and  that  congestion  of  the  kidneys,  within 
physiological  limits,  produces  increased  secretion  of  urine. 


Chapter  XXXV. 


LIQUID  AIR, 
ITS  PROPERTIES  AND   USES 


785 


LIQUID    AIR,   ITS    PROPERTIES   AND    USES. 

Air  is  the  vapor  of  a  liquid,  and  acts  in  its  properties  like 
the  vapor  of  other  liquids.  Each  of  its  constituents,  nitrogen, 
oxygen,  carbon  dioxide,  argon,  and  helium,  is  also  the  vapor  of 
a  liquid. 

In  their  combination,  forming  elementary  portions  of  our 
atmosphere,  apart  from  the  vapor  of  water,  their  physical  prop- 
erties probably  combine  or  mix  in  proportion  to  their  parts  to 
produce  an  average  property  as  found  in  physical  experiments 
with  air.  It  liquefies  at  a  pressure  of  573  pounds  per  square 
inch  at  the  reduced  temperature  of  — 220''  F.,  and  upon  a  gradual 
release  of  pressure  commences  to  boil  with  a  falling  tempera- 
ture. Under  a  pressure  of  294  pounds  it  boils  at  — 240°  P.,  and 
at  atmospheric  pressure  boils  at — 312°  P..  at  which  tempera- 
ture it  can  be  handled  like  water  and  used  for  the  exhibition 
of  the  effects  of  extreme  cold,  and  under  special  conditions  has 
been  used  as  an  element  of  power. 

When  confined  and  its  temperature  rises,  the  pressure  rises 
with  the  temperature  until  at  ordinary  atmospheric  mean  tem- 
perature it  generates  a  pressure  of  12,000  pounds  per  square 
inch.  The  specific  gravity  of  liquid  air  at  its  boiling  tempera- 
ture is  .94  (water  i.oo),  its  latent  heat  about  144  heat  units  per 
pound — by  Dickerson's  experiments,  123  heat  units  per  pound. 
The  critical  point  for  air,  or  the  temperature  above  which  it 
will  not  liquefy  b}-  increased  pressure,  is  — 220°  P.  The  phe- 
nomena of  the  critical  temperature  have  been  stated  as  .hat 
"  there  are  for  every  vaporizable  liquid  a  certain  temperature 
and  pressure  at  which  it  may  be  converted  into  the  aeriform 
state  in  the  same  space  occupied  by  the  liquid ;  indicating 
that,  above  a  certain  temperature  (its  critical),  a  gas  or  air  can 


788  COMPRESSED    AIR    AND    ITS    APPLICATIONS. 

be  squeezed  down  to  the  volume  of  its  mass  as  a  liquid  without 
liquefying."  The  relative  volume  of  free  air  at  mean  atmos- 
pheric temperature  is  about  800  times  its  liquid  volume.  Air 
has  been  compressed  to  14,000  pounds  per  square  inch,  without 
signs  of  liquefying  at  ordinary  temperatures,  and  has  been  used 
at  9,000  pounds  pressure  for  blasting  rock  and  coal. 

It  has  been  claimed  that  Johann  Naterer  of  Vienna,  Austria, 
produced  air  pressures  of  nearly  60,000  pounds  per  square  inch 
— which  is  about  the  tensile  strength  of  open-hearth  steel  and 
twice  the  initial  pressure  of  exploded  powder  in  a  gun — without 
signs  of  liquefying.  Its  density  at  this  pressure  is  stated  by 
Dewar  to  be  1.25  (water  i.oo).  Almagat  also  carried  air  press- 
ures up  to  45,000  pounds  per  square  inch;  and  as  nothing  is 
stated  in  regard  to  temperature,  it  is  assumed  in  both  cases  that 
the  critical  temperature  prevented  liquefaction. 

When  air  is  liquefied  and  allowed  to  boil  off  at  atmospheric 
pressure,  the  nitrogen  boils  off  faster  than  the  oxygen,  and  the 
resulting  free  air  becomes  richer  in  oxygen. 

Pure  metals,  as  stated  by  Dewar,  seem  to  have  no  electrical 
resistance  at  temperatures  near  absolute  zero.  The  electric 
conductivity  of  carbon  decreases  with  low  temperatures  and  in- 
creases with  high  ones ;  at  the  temperature  of  the  electric  arc  it 
appears  to  have  no  resistance. 

The  color  of  liquid  air  is  light  blue. 

Its  use  in  physical  experiments  has  been  a  most  important 
one  in  developing  the  action  of  intense  cold  on  the  tenacity  of 
metals,  in  chemical  reaction  and  magnetic  effect  under  temper- 
atures approaching  that  of  interplanetary  space. 

The  lowest  temperature  as  yet  artificially  produced  was  ob- 
tained in  the  experiments  of  Professors  Dewar  and  Wroblewski 
by  the  evaporation  of  liquid  air  by  which  a  temperature  of 
— 346°  F.  was  reached,  or  within  115°  of  the  reputed  absolute 
zero;  beyond  which,  it  is  claimed,  molecular  vibration  ceases 
and  the  chemical   action  between  all  substances  is   in  abeyance. 

In  physical  investigation  the  convenience  for  obtaining  and 


LIQUID    AIR,    ITS    PROI'KRTIES    AND    USES.  789 

maintaining  intensely  low  temperatures  for  a  considerable  time, 
or  sufficient  for  the  manipulation  of  experiments  in  physical 
phenomena,  is  only  of  recent  date,  and  this  has  opened  the  way 
for  the  most  noted  expansion  in  the  paths  of  physical  research. 

The  action  of  extreme  cold  on  the  tenacity  of  metals  has  be- 
come a  most  interesting  inquiry,  with  results  greatly  contrast- 
ing with  former  theories,  and  tending  to  show  a  critical 
temperature  in  the  tenacity  of  metals  not  uniform,  but  widely 
varying  with  their  crystalline  structure. 

Thus  with  steel,  iron,  copper,  brass,  German  silver,  gold, 
silver,  tin,  and  lead,  the  tenacity  has  been  found  to  be  largely 
increased  from  60°  F.  to — 295°  F.,  mostly  equal  to  50  per  cent, 
and  in  the  case  of  iron  to  more  than  100  percent;  while  the 
highly  crystalline  metals,  zinc,  bismuth,  and  antimony,  lose  half 
their  strength  at  the  lowest  temperature. 

A  singular  incident  is  the  increase  in  the  tensile  strength  of 
the  fusible  alloy  of  tin,  lead,  and  bismuth  of  300  per  cent  at  this 
low  temperature.  ■ 

The  behavior  of  a  magnet  at  the  temperature  of  boiling 
liquid  air  has  been  found  to  be  somewhat  erratic,  owing  prob- 
ably to  the  difficulties  attending  such  experiments;  but  with 
final  results  of  an  increase  of  from  30  to  50  per  cent  of  its  mag- 
netic strength  by  the  extreme  cooling  process. 

In  chemical  research  the  field  of  operation  at  extreme  low 
temperatures  is  so  new  that  but  few  results  of  a  positive  charac- 
ter have  been  reached,  owing  to  the  chemical  inertness  of  all 
the  active  elements,  as  with  acids  and  alkalies. 

At  the  lowest  temperature  yet  reached,  nitric  acid  has  no 
action  upon  metals,  and  acids  and  alkalies  may  be  mixed  with- 
out evolution. 

A  most  curious  physical  phenomenon  is  shown  in  the  condi- 
tion of  meats  at  the  extremely  low  temperature  derived  from 
the  evaporation  of  liquid  air ;  mutton  becomes  so  exceedingly 
hard  that  it  rings  like  porcelain  when  struck  with  an  iron  rod, 
and  may  be  crushed  into  a  fine,  dry  powder  with  a  hammer,  in 


790  COMl'RESSED    AIR    AND    ITS    APPLICATIONS. 

which  muscle,  fat,  and  bone  are  undistinguishable,  but  mingled 
as  dry  sand. 

Professor  McKendrick,  in  England,  has  found  that  microbic 
life  in  flesh  is  so  tenacious  that  it  cannot  be  frozen  out,  even 
after  exposure  to  — 133°  F.  for  four  days;  that  on  thawing  and 
raising  to  normal  temperature,  and  moisture,  activity  of  life  is  at 
once  manifested. 

A  tablespoonful  of  liquid  air  poured  on  about  a  fluid  ounce 
of  whiskey  will  freeze  it  at  once  into  flat  scales,  giving  the 
whole  the  appearance  and  color  of  cyanide  of  potassium.  This 
may  be  emptied  out  on  a  table,  and  will  remain  frozen  in  that 
condition  for  fully  five  minutes. 

One  thing  that  impresses  one  is  that  while  all  molecular  mo- 
tion is  practically  arrested  at  this  temperature,  the  odor  is  per- 
fectly distinct,  showing  that  these  particles  which  stimulate  the 
sense  of  smell  are  active  and  independent  of  the  temperature. 

A  teacupful  of  liquid  air  poured  on  top  of  a  tank  of  cold 
water  goes  into  its  spheroidal  state  instantly,  in  globules  of 
about  half  the  size  of  an  ordinary  marble,  which  fly  around  on 
the  surface,  leaving  a  trail  of  white  vapor  behind  them. 

A  handkerchief  of  either  silk,  linen,  or  cotton,  saturated 
with  the  liquid,  will  be  charred  and  destroyed  just  the  same  as 
if  it  were  put  in  an  oven  and  browned,  though  no  change  of 
color  is  apparent.  Its  evaporation  is  quite  slow,  and  it  may  be 
carried  about  for  a  number  of  hours  in  an  open  vessel  without 
entirely  disappearing.  Absolute  alcohol  solidifies  at  — 203°  F. 
becoming  viscous  before  solidification  like  a  heavy  oil  in  appear- 
ance. 

Professor  Dewar  has  found  that  liquid  air,  when  reduced  to 
its  lowest  attainable  temperature  by  boiling  under  a  vacuum, 
becomes  apparently  solid  or  frozen  ;  and  that  when  the  solid 
mass  is  placed  in  a  strong  magnetic  field,  oxygen  is  drawn  out 
toward  the  poles  of  the  magnet  in  a  liquid  form,  showing  that 
nitrogen  may  be  frozen  at  about  — 346°  F.  The  temperature 
for  freezing   liquid   oxygen   has  not    yet  been  reached.     The 


LIQUID    AIR,    ITS    PROPERTIES    AND    USES. 


/9I 


Vacuum 


■Rubber 
Stopper 


evaporation  of  liquid  air  greatly  increases  its  proportion  of  oxy- 
gen, and  the  liquid  becomes  a  vigorous  element  in  combustion 
even  to  explosive  violence.  Any  fibrous  combustible  material, 
saturated  with  it,  burns  with  explosive  violence.  When  cotton 
fibre  is  wet  with  oil  and  with  concentrated  liquid  air,  and  con- 
fined in  an  iron  tube  or  blast- 
ing-hole, it  explodes  on  firing 
with  all  the  force  of  dynamite. 

The  experiments  on  the 
properties  of  liquid  air  and  its 
bearings  upon  the  properties 
of  all  the  elements  of  nature 
are  in  progress  and  promise 
wonderful  development  in  the 
knowledge  of  their  chemistry 
and  physical  relations. 

There  are  many  beautiful 
experiments  that  illustrate  the 
properties  of  liquid  air  that  we 
do  not  feel  justified  in  giving 
in  this  work.  One  illustrates 
the  phenomenon  of  boiling 
liquid  air  under  a  vacuum  in 
a  test  tube,  which  produces  so 
low  a  temperature  that  air  in 

contact  with  its  surface  liquefies  and  drops  from  its  bottom 
like  rain,  while  the  moisture  in  the  air  is  deposited  on  the  sur- 
face of  the  tube  like  snow. 

The  commercial  production  of  liquid  air  is  a  very  important 
discovery,  and  the  future  question  of  economy  in  motive  power 
may  be  intimately  associated  with  this  liquid.  Compressed  air, 
at  pressures  ranging  from  1,000  pounds  upward,  is  conducted 
from  an  air  receiver  through  a  small  pipe,  is  refrigerated  to  ex- 
pel its  moisture,  and  is  then  conducted  into  the  apparatus  which 
liquefies  it  completelv,  without  the  use  of  chemicals  of  an}'  kind, 


Outside  Covered 
with  Snow 
(Moisture  inAir) 


Fig. 


—LIQUID    AIR    DROPl'IN'G    FRoM    THE 
OUTSIDE   OF   A    TEST  TUBE. 


792  COMPRESSED    AIR    AND    ITS    API'LICATIONS. 

and  it  flows  from  this  apparatus  in  a  stream  about  the  size  of  a 
lead  pencil  (in  the  apparatus  of  Linde)  into  a  glass  insulated  re- 
ceptacle, containing  about  two  gallons.  This  receptacle  was 
filled  in  a  very  short  time.  Of  course,  being  in  an  open  vessel, 
liquid  air  has  no  pressure,  but  its  temperature  is  approximately 
— 315°  F.,  or  375°  below  the  atmosphere  at  60°  F.  Inasmuch 
as  it  boils  rapidly  on  the  surface,  owing  to  its  absorption  of  heat 
from  the  atmosphere,  it  looks  like  milk  on  the  surface,  but  upon 
dipping  some  of  it  out  in  a  glass  and  observing  its  color  through 
the  glass,  it  has  very  much  the  appearance  of  ordinary  water. 
Its  temperature  is  very  deceptive,  for  as  it  runs  from  the  con- 
denser one  may  allow  it  to  trickle  over  the  fingers  for  a  short 
space  of  time,  and  it  appears  to  have  the  atmospheric  temper- 
ature. The  truth,  however,  of  the  matter  is  that  it  does  not 
come  in  contact  with  the  fingers  at  all;  the  hand  being  some- 
thing like  480''  warmer  than  the  liquid,  it  throws  the  liquid 
into  a  spheroidal  state  and  interposes  between  it  and  the  fin- 
gers a  film  of  atmospheric  air.  The  sensation  is  very  much 
like  pushing  one's  hand  into  a  bag  of  feathers  or  into  a  mercury 
bath,  allowing,  of  course,  for  the  difference  in  weight  between 
the  mercury  and  the  liquid  air.  If,  however,  you  immerse 
your  hand  in  the  liquid  a  sufficient  time  to  establish  a  contact, 
"the  flesh  would  be  burned,  the  same  as  if  it  were  exposed  to 
440°  of  heat,  measured  above  the  atmospheric  temperature.  If 
a  test  tube  of  i^  inches  diameter,  having  a  couple  of  pounds 
■of  mercury  in  the  bottom,  is  immersed  in  liquid  air,  the  mer- 
cury will  be  frozen  solid  in  a  few  seconds,  and  may  be  ham- 
mered out  and  otherwise  manipulated  the  same  as  lead.  An 
alcohol  thermometer  of  large  size  will  be  frozen  instantly  upon 
being  immersed  in  the  liquid. 

An  idea  of  the  tremendously  low  range  of  temperature  may 
be  gathered  from  the  fact  that  it  will  take  several  minutes  to 
thaw  out  the  small  bulb  of  this  thermometer  by  covering  it 
with  the  palm  of  the  hand. 

In   Fig.  539  is  shown  an   ideal  view  of  the  "Linde"  liquid- 


LI(^)UIl)    AIR,    ITS    PROPERTIES    AND    USES. 


793 


air  apparatus  in  its  earlier  form,  in  which  the  air  at  atmospheric 
pressure  and  temperature  was  taken  into  the  compressor  A  and 
delivered  to  the  cooler  />,  at  from  250  to  500  pounds,  where  it 
was  cooled  to  as  low  temperature  as  the  means  would  allow; 
then  entering  the  inner  of  the  double  concentric  coil  C.  it  was 
delivered  at  the  needle  valve  D,  where  its  expansion  into  the 
receiver  E  was  regulated.  Its  expansion  to  nearly  atmospheric 
pressure  produced  a  very  low  temperature,  but  not  low  enough 
for  liquefaction  ;  but  as  the  cold  air  was  exhausted  from  the  re- 
ceiver through  the  annular 
space  between  the  coils,  it 
cooled  the  incoming  air  to  such 
a  degree  that  its  own  expansion 
carried  the  temperature  to  the 
required  point  for  liquefaction, 
in  which  state  it  was  deposited 
in  the  receiver  to  be  drawn 
off  at  the  faucet.  This  was  a 
negative  or  cold  refrigerative 
process,  but  the  final  cold  ex- 
haust was  wasted  at  F. 

In  Fig.  540  is  shown  a 
further  improvement  of  Dr. 
Linde's  liquid-air  apparatus, 
by  turning  the  cold  air  ex- 
haust    into     the    compressor, 

thus  enabling  a  colder  delivery  from  the  compressor  and  a 
colder  delivery  of  the  air  stream  from  the  cooler  by  adding  ice 
to  its  cooling  water.  This  was  called  the  continuous  process, 
by  which  all  the  exhaust  was  used,  and  as  much  fresh  com- 
pressed air  drawn  in  at  A  in  the  illustration  as  would  supply 
the  loss  by  liquefaction. 

In  the  Linde  apparatus,  as  shown  in  our  illustration,  cold 
compressed  air  at  324  pounds  per  square  inch  is  furnished  to 
the    apparatus    at    A,   which    establishes    through    the    suction 


Fig.  339  — lixde  liquid-aik  apparatus. 


794 


COMPRESSED    AIR    AND    ITS    APPLICATKJ.NS. 


pipe  and  outer  coil  a  back  pressure  in  the  liquefying  flask  T 
of  about  325  pounds  per  square  inch. 

The  compressor  P  is  of  the  kind  used  for  liquefying  car- 
bonic acid  gas ;  it  raises  the  pressure  from  the  suction  side  of 
324  pounds  to  955  pounds  on  its  force  side,  from  which  the  ex- 


^i^a 


Fig.  540. -the  lixde  regenerativ^e  liquid-air  system. 


pansion  is  obtained  for  producing  the  low  temperature  required 
in  the  flask  T. 

In  subsequent  experiments  a  pressure  of  3.000  pounds  per 
square  inch  has  been  used. 

The  high-pressure  air  pipe  enters  the  refrigerator  ./  into  a 
coil  immersed  in  a  circulating  current  of  cold  brine  at  about  10° 
F.,  which  reduces  the  tem.perature  of  the  high-pressure  air  to 
about  15°  F.  The  high-pressure  pipe  then  enters  and  is  en- 
closed in  the  exhaust  pipe  of  the  apparatus  in  a  coil  containing 
260  feet  of  I  3-^ -inch  pipe,  the  internal  pipe  size  not  stated,  but 
probably  -)^-inch  pipe.  The  small  pipe,  emerging  from  the 
large  coil  at  the  bottom,  enters  the  liquef3nng  flask  w'ith  a  regu- 
lating valve,  as  .shown  in  the  cut.      The  regenerating  coil  and 


LIQUID    AIR,    ITS    PROPERTIES    AND    USES.  795 

flask  being  enclosed  in  a  thoroughly  insulated  chamber,  the 
operation  may  be  as  follows : 

Taking  the  air  from  the  primary  compressor  at  324  pounds 
pressure  and  at  normal  temperature  or  less  by  artificial  cooling, 
say  to  30°  F.,  the  high-pressure  compressor  carries  the  pressure 
with  a  third  of  its  previous  volume  to,  say,  972  pounds,  which 
w^ill  raise  the  theoretical  temperature  to,  say,  520°  F. 

This  temperature  should  be  so  much  absorbed  by  the  re- 
frigerator J  as  to  allow,  at  the  start  of  the  machine,  of  a  tem- 
perature below  the  normal  at  the  expansion  nozzle  in  the  flask. 
The  expansion  of  the  air  from  972  pounds  to  324  pounds,  say 
3  volumes,  or  43  atmospheres,  reduces  the  temperature  by  ex- 
pansion, theoretically,  to  about  400°  below  zero  F.  ;  but  in  con- 
sideration that  the  material  of  the  apparatus  is  at  normal  tem- 
perature and  the  specific  heat  of  air  being  of  low  degree,  a  large 
part  of  this  excessive  cold'must  be  absorbed  in  the  material  of 
the  apparatus  and  its  insulation,  in  order  to  bring  the  whole 
apparatus  down  to  a  productive  temperature.  This  can  be  done 
only  by  operating  the  air  in  a  cycle,  by  which  the  cold  pro- 
duced by  expansion  in  the  flask  is  utilized  in  the  outer  coil  for 
reducing  the  temperature  of  the  air  in  the  inner  coil.  The 
time  required  for  cooling  the  insulated  apparatus  to  the  temper- 
ature for  producing  liquid  air  in  the  flask  w^as  found  to  be  five 
hours ;  wdien  the  machine  became  a  constant  producer  of  liquid 
air  at  the  rate  of  six  pounds  per  hour. 

According  to  Linde — perhaps  its  mo.st  successful,  experi- 
enced, and  reliable  producer — it  requires  100  horse-power  at 
the  compressor  to  produce  as  many  pounds  of  liquid  air  per 
hour,  and  it  can  develop  but  a  fraction,  probably  a  small  frac- 
tion, of  that  amount  of  power  in  regasifying.  It  loses  by  sim- 
ple vaporization,  even  in  large  vessels,  10  gallons  and  upward, 
about  4  per  cent,  under  the  most  favorable  conditions  for  its 
preservation,  each  hour.  Its  efficiency  in  the  motor  is  found  to 
be  about  4  per  cent ;  that  of  the  steam  engine  is  from  7  to  20  and 
more,  and  that  of  the  gas  engine  ranges  to  still  higher  figures. 


■gO 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


In  the  Dewar  liquid-air  apparatus  illustrated  in  Fig.  542,  car- 
bonic acid  is  used  in  its  liquid  state  for  producing  the  primary 
cold  by  its  evaporation  and  expansion  in  a  helical  coil  inter- 
locked with  the  inlet  air  coil  in  an  insulated  cylinder. 


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The  liquid  carbonic  acid  enters  the  apparatus  at  B,  passes 
through  the  helical  coil  indicated  by  the  black  dots,  and  expands 
from  the  needle  valve  in  the  centre  chamber,  which  is  regu- 
lated by  the  stem  and  wheel  at  C. 


LIQUID    AIR,    ITS    PROPERTIES   AND    USES. 


797 


The  expanded  gas  at  a  very 
low  temperature  permeates  the 
whole  interior  system  of  air  coils 
and  exhausts  around  the  pri- 
mary inlet  coils  at  H.  The  air, 
compressed  to  1,500  pounds  per 
square  inch,  enters  at  A,  and 
is  cooled  by  the  exhaust  of  the 
carbonic-gas  exhaust  in  the  outer 
section,  and  further  cooled  by 
the  cold  gas  surrounding  the  air 
coil  in  the  inner  section,  and 
is  finally  expanded  at  a  very 
low  temperature  from  the  needle 
valve,  liquefying  a  portion,  while 
the  excess  of  cold  air  at  the  liq- 
uefying temperature  is  exhausted 
from  the  receiver  G  through 
the  annular  space  containing  the 
last  section  of  the  air  coil. 

In   this  process  advantage  is 
taken   of   the   extreme    cold-pro- 
ducing power  of  expanding  carbonic  acid,  and  also  of  the   re 
generative  power  of  the  final  ex  pansion  of  cold  compressed  air 


Fig. 


THE     DEWAR     AIR-EIQUEFVING 
APPARATUS. 


THE  LIQUID-AIR  PLANT  OF  THE  GENERAL  LIQUID  AIR  AND 
REFRIGERATING  COMPANY  OF  NEW  YORK,  OPERATING  UNDER 
THE    PATENTS    OF    O.   P.   OSTERGREN   AND    MORIZ    BURGER. 


The  plan  (Fig.  543)  shows  the  passage  of  the  air  from  the 
outside  through  a  four-stage  compression  with  intercoolers, 
cleaner,  and  separator,  at  which  point  the  air  pressure  is  1,200 
pounds  per  square  inch.  So  far  the  operation  is  identical  with 
any  four-stage  air-compressing  plant. 

Continuing  the  circuit  from  the  after-cooler,  the  air  enters  a 


■98 


COMPRESSED    AIR   AND    ITS    API'LICATIONS. 


Stea  m 
Cylinder 


Steam 
Cylinder 


separator  for  the  purpose  of  removing  all  moisture,  oil,  dust,  or 
other  impurities.  Passing  on,  the  air  enters  the  eompressed-air 
coils  in  the  brine  or  cooling  tank,  a  section  of  which  is  shown 
_  in  Fig.  544,  which  is  a  plan 

of  the  interlocking  coils  of 
compression  and  expansion. 
The  compressed  cold  air  en- 
tering the  coil  at  E  and 
ide  through  the  coil  to  the  cen- 
tral header  at  A',  is  expand- 
ed through  a  needle  valve 
into  the  liquefier,  and  the 
remaining  exhaust  returned 
to  the  second  central  header 
E,  and  through  the  spiral 
interlocking  coil  to  the 
outer  header  X.  The  ex- 
pansion valve  is  so  adjusted 
as  to  throttle  the  air  flow 
and  keep  the  difference  of 
pressure  on  its  two  sides  at 
about  900  pounds.  This 
drop  in  pressure  and  consequent  expansion  cool  the  air  to  a 
certain  extent. 

The  cooled  air  passes  upward  in  the  exhaust  passage  of  the 
central  header  at  E,  and  through  and  around  the  expanding 
spiral  coils  to  the  outlet  to  the  brine-tank  coil.  Thus  the  in- 
coming compressed  air  is  cooled  by  the  brine  contact,  which 
in  turn  is  cooled  by  the  expanding  air  in  the  interlocked  ex- 
haust coils. 

This  accumulative  cooling  continues  until  eventually  the 
critical  temperature  of  air  is  reached.  Then,  and  then  only,  a 
portion  of  the  air  passing  through  the  expansion  valve  liquefies 
and  collects  in  the  small  chamber  over  the  second  or  after-cooler, 
or  reservoir  valve,  shown  in  section,  lower  part  of  Fig.  545. 


Builers 

Fig.  543.— liquid- air  plant. 


LIQUID    AIR,    ITS    rROI'ERTIKS    AM)    USES. 


799 


Tf'ond  Lagging 


That  portion  which  does  not  liquefy,  which  is,  however,  in- 
tensely cold,  of  course  passes  into  the  cooling  tubes  as  before. 

From  what  has  been  said  it  will  be  seen  that  the  system  is  a 
regenerative  one  and  that  the  air  once  taken  into  the  system  is 
used  over  and  over.  There  is,  of  course,  need  for  new  air  to 
take  the  place  of  that  liquefied,  and  this  is  drawn  in  from  out- 
side through  the  cleanser,  shown  in  Fig.  543,  by  the  bv-pass 
from  the  cleanser  to  the  low-pressure  cylinder  of  the  compressor 
with  a  suitable  automatic  valve.  This  cleanser  consists  of  an 
inlet  tube  coming  from  the  roof  of  the  building,  and  extending 
down  to  the  bottom  of  the  containing  tank.  From  the  bottom 
of  the  four  arms,  the  air  bubbles  out  and  up  through  water  to  a 
coke  filter,  where  it  is  thoroughly  scrubbed.  It  is  also  subjected 
to  a  water  spray,  after  which  it  remains  in  the  upper  portion  of 
the  tank  until  needed  by 
the  system,  when  it  is 
drawn  into  the  low- 
pressure  cylinder. 

Returning  to  the  liq- 
uefier  again,  it  will  be 
seen  that  opening  the 
after-cooler  valve  allows 
the  liquefied  air  to  pass 
into  the  reservoir  below, 
where  at  first  it  will 
immediately  volatilize, 
owing  to  this  portion  of 
the  apparatus  being 
warm.  This  will  produce  in  the  reservoir  sufficient  pressure  to 
lift  the  heavy  inverted  cap  and  permit  the  intensely  cold  air  to 
flow  out  into  the  vacuum  space  of  the  after-cooler,  and  thence 
through  the  spiral  space  of  the  liquefier.  At  the  same  time  a 
portion  of  the  cold  air  will  pass  through  the  coiled  siphon  tube 
and  out  the  draw-off  valve.  Soon  the  parts  of  the  after-cooler 
become  sufficiently  chilled,  and  the  liquid  air,  passing  through 


Fir,.    544. -PLAN    OF   BRINE   TANK. 


8oo 


COMPRESSED    AIR    AND    ITS    APPLICATIONS. 


the  lower  valve,  remains  in  a  liquid  state.  The  heavy  cap  is  so 
proportioned  that  there  is  a  pressure  of  about  6  pounds  per 
square  inch  on  the  liquid  surface,  and  this  is  sufficient  to  force 
the  liquid  air  through  the  siphon  tube  and  out  of  the  faucet. 
We  then  have  the  following  condition  of  affairs: 


Fig.  545  — sectmn.    brine  tank,  expansion  valve,  i.iquefino  chamber,  and  liquid-air 
keservoir  or  aeter-co(  )ler. 


The  reservoir  is  partially  filled  with  liquid  air,  as  is  also  the 
coils  of  the  after-cooler,  and  the  space  surrounding  the  tubes  is 
constantly  being  exhausted,  so  that  whatever  liquid  air  or  vapor 
air  may  spill  over  when  the  inverted  cap  lifts,  is  instantly  evap- 
orated in  and  around  these  filled  tubes,  thus  further  reducing 
the  temperature  of  the  air  about  to  be  drawn  off:  the  vacuum 


LIQUID    AIR,    ITS    PROPERTIES   AND    USES.  80I 

spiral  space  surrounding  the  tubes  of  the  liquefier  is  constantly 
having  the  intensely  cold  evaporated  air  passing  through  it,  and 
the  temperature  of  the  whole  apparatus  is  therefore  being  grad- 
ually reduced  toward  some  minimum,  which  so  far  as  present  in- 
dications go  is  remarkably  near  absolute  zero. 

One  of  the  problems  to  be  solved,  before  liquid  air  can  be  of 
any  great  commercial  value,  is  some  method  of  carrying  and 
vStoring  the  material  so  that  it  can  be  retained  in  a  liquid  form. 
The  company  has  endeavored  to  perfect  this  feature  in  a  practi- 
cal and  business-like  way. 

The  result  of  the  company's  efforts  in  this  line  is  the  con- 
struction of  metallic  tanks  of  various  sizes  up  to  40  gallons 
capacity,  in  which  an  inner  metallic  vessel  is  inclosed  except 
for  a  small  offset  pressure-gauge  tube,  and  the  larger  opening 
constituting  at  the  same  time  the  filling  tube  and  the  relief 
valve.  Surrounding  this  is  a  second  vessel,  in  its  turn  sur- 
rounded by  some  non-conducting  material  such  as  corn  pith, 
excelsior,  granulated  cork,  or  the  like,  contained  in  a  wicker 
basket.  The  inner  tank  being  filled  with  liquid  air,  the  relief 
valve  automatically  opens  slightly  from  time  to  time,  as  the 
pressure  exceeds  about  6  pounds,  and  permits  the  escape  of  the 
cold  air  into  the  space  between  the  two  metallic  tanks.  This 
forces  the  warmer  air  out  through  the  bottom  of  the  tank  and 
maintains  a  very  cold  blanket  of  air  between  the  liquid  air  and 
the  exterior  insulating  casing;  smaller  and  cheaper  forms  are 
made  by  using  an  open  inner  vessel  made  of  wood  pulp  similar 
to  the  well-known  one-piece  water-buckets.  These  are  sur- 
rounded by  wire  netting  held  away  by  small  wooden  strips. 
The  vessel  is  then  put  in  a  wicker  basket,  packed  about  with 
some  insulating  material  as  in  the  former  case,  and  is  provided 
with  a  wooden  cover  which  rests  on  the  wire  netting  and  forms 
an  air  space. 

Still  another  form  consists  of  two  metallic  spheres,  between 

which  is  a  third  moulded  cork  sphere  held  away  from  the  others. 

Both  the  inner  and   outer  spheres  are  provided  with  separate 
51 


802  COMPRESSED    AIR   AND    ITS    APPLICATIONS. 

relief  valves,  so  that  when  the  pressure  exceeds  a  certain  set 
amount  the  inner  valve  lifts  and,  one  might  say,  exhales  into 
the  space  between  the  inner  and  the  cork  sphere.  The  cold  air 
gradually  works  outward  through  the  cork,  becoming  warmer 
as  it  progresses.  Finally  it  reaches  the  space  between  the  cork 
shell  and  the  outer  metal  casing  and  accumulates  until  the 
pressure  is  sufficient  to  lift  the  second  valve,  when  it  passes  into 
the  surrounding  atmosphere. 

While  the  company  has  devoted  its  chief  endeavors  to  the 
process  of  liquid  air  manufacture  and  transportation,  it  has  also 
paid  some  attention  to  the  possible  applications  of  liquid  air. 
One  which  is  of  especial  interest  in  the  summer  days  is  the 
operation  of  a  cooling  fan  by  compressed  air  obtained  from 
volatilizing  liquid  air.  The  liquid  is  held  in  a  suitable  recep- 
tacle, while  a  coil  connected  with  this  receptacle  constitutes  a 
vaporizer  and  heater  utilizing  the  heat  of  the  atmosphere. 
The  fan  is  revolved  by  a  small  turbine  driven  by  the  air  under 
pressure,  which,  as  it  escapes  from  the  motor,  is  caught  by  the 
fan  blades  and  whirled  forward  in  the  current  of  air.  In  this 
way  not  only  is  the  air  in  a  room  kept  in  constant  motion,  but 
it  is  continally  cooled  and  freshened  by  the  addition  of  the  cold 
exhaust  air  of  the  motor. 


Chapter  XXXVI. 


PATENTS 


803 


PATENTS. 

ISSUED    BY  THE  UNITED  STATES    PATENT  OFFICE    ON    COMPRESSED 
AIR  AND    ITS  APPLIANCES,    FROM    1 875    TO    JULY    I,    I9OI. 


1875. 

Air  Engine— Rider 167,568 

Air  Engine — Tiider 158,525 

Air  Engine— Riley 165,027 

Air  Compresscn- — Bailej' 161,090 

Air  Compressor — Corobbi  &  Bel- 
lini  159,075 

Air  Brake^ — .lames 165,235 

Air  Brake—Tones 166,386 

Air  Brake— Ladd   165,337 

Air  Brake— Moschcowitz 166,026 

Air  Brake— Perrine 166,404 

Air  Brake— Perrine 166,405 

Air  Brake— Perrine 166,406 

Air  Brake — Perrine 169,575 

Air  Brake — AVestinghouse 162,465 

Air  Compressor— Reynolds 160,956 

Air  Engine— Connolly 164,809 

1876. 

Air  Engine— Sclmake 184,913 

Air  C-onipressor — -Crocker.  ....  ..176,931 

Air  Compressor — Fnlton 177,495 

Air  Compressor — Hill. 171,805 

Air  Compressor — Laurence 172,751 

Air  Compressor — ]Manz 176,795 

Air  Brake— Cluuhvick 180.460 

Air  Brake— Reniff 183.206 

Air  Brake — Westinghouse 175,886 

Air  Brake— Westinghouse 180,179 

Air  (Compressor— Sawtell 183,596 

Air  Compressor — Seal ...  .174,860 

Air  Compressor— Seal 182,333 

Air  Compressor — Sturgeon 180,958 

Air  Com]»ressor — Tallmau 176,096 

1877. 

Air  Compressor— Babbitt 198,067 

Air  Compressor — Clayton 186,306 

Air  C'Ompressor — Garrison 186,336 

Air  Brake— Green  et  al 198,015 

Air  Brake— Stevens 191,261 

Air  Compressor— Reynolds. .' 187,906 

Air  Compressor — Root 196.253 

Air  Engine— Allen 193,631 

Air  Engine — Davey 186,119 

Air  Engine— Ilock  &  Martin 190,490 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
xVir 
Air 
Air 
Air 
Air 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


1878. 

Engine— McKinley 206.597 

Engine— Rider. . ." 206,356 

Engine— Ward 198,827 

Compressor — Doremus 207,954 

Compressor — Dreyfus 200,901 

Compressor— Frizell 199,819 

Brake— Knapp 204,440 

Brake— Maxwell 207,126 

Brake— Newton 202,368 

Brake— Prince 204.914 

Brake— Raoul 203,647 

Compressor— Springer 211,062 

1879. 

Engine- Rider 220,309 

Engine— Sherrill 213,783 

Compressor — Clayton 222,014 

Compressor — Clayton 220,123 

Compressor — Gardner 221,802 

(Compressor — Harvey 211,570 

Compressor— .Tackson 218,029 

Compressor — .Jolmstcm 221,318 

Compressor — Moore 216,211 

Brake— Osgood 212,972 

Brake— Schultz 220, 178 

Brake— Westinghouse 214,603 

Compressor — Pitchford 215,540 

Comijressor — Spencer 214,465 

Compressor— '■I'atham 222,802 

Compressor — Thomas 217,834 

Compressor — Treat 221,126 

Engine— Eckart 216,563 

Engine— Hardie  &  James 216,611 

Engine— Mathes 314,050 

1880. 

Engine— Presbrey 231,446 

Engine — Thuemnder 232,660 

Engine — -Thuemmler 233,125 

i:n!iine— Woodbury  et  al 228,712 

Engine- AVoodbury  et  al. .  .  .228,713 
Eno-ine — Woodbury  et  al. . .  .228,714 

Engine— Woodburj'  et  al 228,715 

Engine — Woodbury  et  al 228.716 

Engine — Woodbury  et  al 228,717 

Compressor — Bois 227,877 

Compressor — Bueil 234,751 

Compressor — Connor  &  Dods. 232,939 


8o6 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Air 
Air 
Ail- 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 

Air 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Compressor— Eckart 224,081 

Compressor— Hill 229,821 

Compressor — Lawrence  et  al.. 226. 918 

Brake— Glenn 234.179 

Brake— Hall 231.311 

Brake — Loughridge 234,134 

Compressor — Parkinson 225,  lol 

Compressor— Pitehford 233,432 

Compressor — Richmaun 229,468 

Compressor — Rix 230,296 

Compressor — Rix 235,816 

Compressor — Sergeant 233,881 

Compressor — Stockman 234,733 

Engine- Beaumont 232,438 

Enffine — Ericsson 226,053 

Engine— Hill 229,821 

1881. 

Compressor — Allen 237,359 

Compressor — Allen 237,360 

Compressor — Boerner 239.310 

Compressor — Buell 246,657 

Comj^ressor — Claj'ton 241,930 

Compressor — Cashier 236,992 

(Compressor — Freeman 238,225 

Compressor— Fitzpatrick. . .  .238,374 

Compressor — Hill 244.127 

Compressor— Hill 244,128 

Compressor — Hill 237,274 

Compressor— Hill 243.257 

Compressor^ — Hudson 241.984 

Compressor — Livingston 242,008 

Compressor — Mayrhofer  .  .  .  .236.713 

Brake— Fames.  /. 241,323 

Brake— Fames 241.325 

Bi-ake- Lorraine 246. 166 

Brake — "Westinahouse 243.415 

Brake— Westinghouse 245.109 

Brake — Westinghouse 245.110 

Compressor — Quinn 236,455 

Compressor — Robinson  &  Ri- 
ser  248,218 

Engine — Lyman 236,954 

1882. 

Engine— Reynolds 262.119 

Compressor — Babcock 253,830 

Compressor — Baker 259.741 

Compressor — Beers 268.854 

Compressor—  Bois 259,799 

Compressor — Bradley 254,915 

Compressor— Hill 261 .606 

Compressor— Hill 261.605 

Compressor — Manning 256,232 

Compressor — ^Mayrhofer  . .  .  .261.560 

Compressor — Monson 257.885 

Brake— Brockway  et  al 264.617 

Brake— Ford 266.684 

Brake — Hanseom 265,671 

Brake — Van  Dusen 269.747 

Compressor — Overton 263.206 

Compressor — Overton 263.207 

Compressor — Rand 255,116 

Compressor — Reynolds 262,119 


Air  Compressor — Sergeant 264,775 

Air  Compressor — Smith 269,730 

Air  Compressor — AVang 255,222 

Air  Compressor — Wang 255,901 

Air  Compressor — "Wang 262,157 

1883. 

Air  Engine — Nash 278,257 

Air  Engine— Wilcox 289,481 

Air  Engine— "Wilcox 289,483 

Air  Compressor— Babcock 280,997 

Air  Compressor — BaT)Cock 287,358 

Air  Compressor — Bennett 283,955 

Air  Compressor — Bicknell 273,014 

Air  Compressor — Cullingworth.  .287,104 

Air  Compressor — Fox 285,748 

Air  Compressor^ — Freeman 290,764 

Air  Compressor — Honigman 288.435 

Air  Compressor — Lawler 272.711 

Air  Brake  (re -issue)— Ford. ......   10.298 

Air  Brake— Reilly 290,269 

Air  Brake— Thaver  et  al 283.534 

Air  Brake— Wes"tinghouse 270.528 

Air  Compressor — ^loore 285.297 

Air  Compressor — Reynolds 272,771 

Air  Compressor — Sturgeon.  ....  .275.959 

Air  Enirine— Boynton 289.967 

Air  Enaine— Cook 271.040 

Air  Engine— Cook 272,656 

Air  Engine— Eimecke 270,036 

Air  Engine— McDonough 278,446 

1884. 

Air  En  cine— Robinson 809,163 

Air  Engine— Stevens 305.114 

Air  Engine — Wilcox  (reissue)...   10.486 

Air  Engine — Wilcox  (re-issue) 10.529 

Air  Compres.sor— Allen 299,314 

Air  Compressor — Bristin 302,978 

Air  Compressor — Chichester 308,061 

Air  Compressor — Cullen 307.443 

Air  Compressor— Ehlers 301.348 

Air  Compressor— Hill 292,814 

Air  Compressor— Krutsch 303.206 

Air  Brake— Dickson 306.140 

Air  Brake— Flad 296. 546 

Air  Brake— Flad 307.535 

Air  Brake— Flad 307.536 

Air  Brake— Green 309.845 

Air  Brake— Masrowan 293.481 

Air  Brake— Mark 307.561 

Air  Brake— Paradise 293.774 

Air  Brake— Sjogren 300.401 

Air  Brake— si oan 307.344 

Air  Brake— Willis 303.777 

Air  Compressor — ^Vloore 309,643 

Air  Compressor — Norris 310,148 

Air  Compressor — Pfanne 295,800 

Air  Endne— Baldwin 292,400 

Air  Engine— Bausman 299.325 

Air  Enffine — Cramer 294.369 

Air  Engine— Eteve  &  DeBraan.  .309.835 

Air  Ensrine — Graham .302.246 

Air  En~!,nne— Leavitt 307.313 

Air  Engine— Maxim 293, 185 


PATENTS. 


807 


1885. 

Air  Engine— McTighe 321,739 

Air  Engine — Pollock 31(),656 

Air  Engine— Shilling 320,182 

Air  Engine— Wilcox 332,812 

Air  Engine— Wood 324,510 

Air  Engine — Woodbury  ct  al. . .  .324.062 
Air  Engine — AVoodbury  el  al. . .  .331,359 
Air  Engine— Woodburj'  el  al. .  .  .331,361 
Air  Engine — AVoodbury  et  al. . .  .324,060 

Air  Engine— Woodbury  et  al 324,061 

Air  Engine- Woodbury  et  al 325,640 

Air  Engine— Woodbury  et  al.. .  ..327,748 

Air  Compressor— Bolton   314,218 

Air  Compressor — Corey 311,100 

Air  Compressor — Erwin 329,377 

Air  Compressor — Erwin 333,208 

Air  Compressor — Fox 321,206 

Air  Compressor — Fox 321,207 

Air  Compressor — Leavilt 320,482 

Air  Brake— Bass 312,245 

Air  Brake— Hans(!om   326,646 

Air  Brake— Hojiper 321,971 

Air  Brake— Me Kiiinev 311,196 

Air  Brake— Sloan . . . '. 327,027 

Air  Brake— Sloan 330,164 

Air  Compressor — Monson 32S,598 

Air  Engine— Bolton 314,218 

Air  Engine — Bausman 313,646 

Air  Engine— Coffleld 322,796 

Air  Engine— Colman 317,093 

Air  Engine— Colman 317,628 

Air  Engine — Corey 311,106 

Air  Engine — Hanover 310,419 

Air  Engine — Hurd 325,805 

Air  Engine— Leavitt 321,985 

Air  Engine — Limpus 329,914 

1886. 

Air  Engine — Rider 345,450 

Air  Engine- Rider 353,004 

Air  Engine— Serdinko 335,388 

Air  Compressor — Chieliester 333,994 

Air  Compres.sor — CvUliugwortli.  .355,002 

Air  Compressor — Depp 333,613 

Air  Compressor — Dow 341,099 

Air  Compressor — Erwin 340,496 

Air  Compre.ssor — Fevrot 336,224 

Air  Compressor — Harrold ;!45,969 

Air  Compressor — Hugentobler.  .  .342,798 

Air  Compressor — .Johnson 349,954 

Air  Compressor — McLean 341,673 

Air  Brake — Easton 354,014 

Air  Brake- Goode 353,446 

Air  Brake— XIaberkorn 335,446 

Air  Brake— Hollerith 334,020 

Air  Brake— Hollerith 334,021 

Air  Brake— Hollerith 334,022 

Air  Brake— Kneeland 351,383 

Air  Brake— Melson .352,927 

Air  Brake— Perkins 345,537 

Air  Brake— Pickering 334,466 

Air  Brake— AVisner  .\ 335,094 

Air  Compressor — Swartz 342,310 


Air  Compressor— Thomas 337,209 

Air  Engine — Babcock 334,153 

Air  Engine — Babcock 334,153 

Air  Engine— Babcock 334,154 

Air  Engine — Lachmann 333,644 

1887. 

Air  Engine— McKinley 356,146 

Air  Engine — McKiidey 356,147 

Air  Engine— Philpott' 359,282 

Air  Engine — Tasker 364,451 

Air  Compressor — Chichester 370,376 

Air  Compressor — •Cunnnings 363,509 

Air  Brake— Bass ! 358,142 

Air  Brake— Cari)eii1er 359,953 

Air  Brake — Hanscom 369,057 

Air  Brake— AVestinghouse 360,070 

Air  Compressor — Strange 373,419 

Air  Engine — Baldwin  it  Bradford 

355,633 
Air  Engine— Ch)se 366,204 

1888. 

Air  Engine— Rider 393,663 

Air  Engine  —Rider 393,723 

Air  Engine— AVinchell 381,313 

Air  Compressor — Chamberlain. .  .376,141 
Air  Compressor — Cullingworth.  .377,481 

Air  Compressor — Dean 380,195 

Air  Compressor— Erwin 3S2,700 

Air  Compressor — Forster 375,929 

Air  Compressor — Forster 376,589 

Air  Compressor — Forster 384,356 

Air  Compressor — Hunter 392,611 

Air  Compressor — Keenan 384,529 

Air  Compressor — McKim 375,761 

Air  Brake— Andrews 385,224 

Air  Brake— Boluss ,382,749 

Air  Brake— Carpenter 378,657 

Air  Brake— Dixon 382,031 

Air  Brake— Dixon 3S9,643 

Air  Brake— Quels 384,686 

Air  Brake— Quels 384,  ()«7 

Air  Brake— Harvey 378.365 

Air  Brake— Lansberg 3S6.640 

Air  Brake— Lansberg 392, S72 

Air  Brake— Lchy 3«1 .392 

Air  Brake— Lewis 3S3.819 

Air  Brake— Park 385,198 

Air  Brake— Park 393,784 

Air  Brake— Solano   376,970 

Air  Brake— Solano 378,628 

Air  Brake— Solano 382,667 

Air  Brake— Solano 387,018 

Air  Brake— Williams 393.950 

Air  Compressor — Nosbaume  .  .  .  .393,172 

Air  Compressor— Pitt 386,028 

Air  Compressor — Iteynolds 378,336 

Air  Engine- Bair.  . .' 389,045 

Air  Engine— Clark 386,454 

Air  Engine— Genty 387,063 

1889. 

Air  Engine— Schmid  &  Beckfel(1.403,294 
Air  Engine— Stevens 414,173 


8o8 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Air  Engine — Woodbury  ct  al 404,237 

Air  Engine— Wright.  /. 408, 7H4 

Air  Compressor — Cuniniings 412,474 

Air  (Compressor — Davey 409,778 

Air  Compressor — Fitzjiatiick.  .  .  .402,517 

Air  Comjiressor — Funk 417,717 

Air  Compressor — Guthrie 417, 4H2 

.'Vir  Brake— Bohiss 414,138 

Air  Brake— Boluss 398,310 

Air  Brake— Collins 400,638 

Airl5rak( — Collins 400,639 

Air  Brake— Dixon 402,418 

Air  Braki — Dixon 412,108 

Air  Brake— Dixon 418,506 

Air  Brake— Daellenbaeh 415,162 

Air  Brake- Ilaberkorn 398,829 

Air  Brake— Ilaberkorn 413,253 

Air  Brake— Holleman 405,705 

Air  Brake — Lausberg 415,513 

Air  Brake — Lansberg 415,514 

Air  Brake — Lansberg 415,515 

Air  Brake — Lansberg 415,516 

Air  Brake— Lansberii- 415,517 

Air  Brake— Lapish.  ^ 399,420 

Air  Brake— Lewis 410,288 

Air  Brake— Mar.sh 396,284 

Air  Brake— Massev 414,717 

Air  Brake— ]Max well 405,968 

Air  Brake— Xorris 413,205 

Air  Brake— Park 407,445 

Air  Brake— Piteliard 410,922 

Air  Brake— Pitehanl  el  al 399,158 

Air  Brake— Pitchard  et  al 399,157 

Air  Brake— Bvmer 416,953 

Air  Brake— Solano 405,855 

Air  Brake— Solano 406,006 

Air  Compressor — Seiaeant 415,822 

Air  Engine— Baldwin 404,818 

Air  Engine— Humes 400,850 

1890. 

Air  Engine— Broek 434,422 

Air  Engine — Eastman 443,641 

Air  Engine — Ericsson 431,792 

Air  Engine- Harder 438,251 

Air  Engine— Metzine- 441,103 

Air  Eno-ine— :\[eCaria 420.824 

Air  Engine— :MeTiglie 429,281 

Air  Engine— :\IeTighe 429,282 

Air  Engine— :\IeTighe 429,283 

Air  Engine — Rogers 427,911 

Air  Engine — Sc-hmid  ct  Beekfeld.421,525 

Air  Engine— Vivian 437,820 

Air  Compressor — Elolieinio 435,034 

Air  Brake— Boluss 435,791 

Air  Brake— Burbank  et  al 428,299 

Air  Brake— Daellenbaeh 442,019 

Air  Brake  (re-issue)— Guels 11,070 

Air  Brake— Guillemet 437,300 

Air  Brake— Harris 442,621 

Air  Brake— Hogan 433,127 

Air  Brake— Hogan   433,594 

Air  Brake — Hoiran 433,595 

Air  Brake- Hopper 430,024 

Air  Brake— Lansberg 439.528 


Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Air 
Air 
Air 

Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Brake— Maher 433,737 

Brake— Martin 437,218 

Brake— Roberts 433.040 

Brake — Robinson 437,800 

Brake— Stewart 420,121 

Brake— Sehroyer 426,144 

Biake— Walker 438,038 

Brake— Westinghouse 421,641 

Brake— Williains 441,526 

Brake— Williams 431,303 

Brake— Williams 431,790 

Brake  (re-issue) — Williams. .  .    11,124 

Brake— Williams 431,304 

Compressor— Hill 4;!9.876 

Compressor — Mas.se}- 433,951 

Compressor — Rand  c\:  Halsey  .421,611 

1891. 

Engine— Benster 463.092 

Engine — Bergman 463,025 

Engine^ — Chapman 447,066 

Engine^ — Griswold 455,201 

Engine— Hall 457,272 

Engine— Hall    457,273 

Engine — .Jefferson.    .     464,364 

Engine — Robinson 445,904 

Engine— Rusk 458,070 

Compressor — Clark 453,374 

Brake— Barnes  et  al 462,193 

Brake  (re-issue) — Bavlev...     11,145 

Brake— Botliwell. .  .\  .^ 456,247 

Brake— Beery 452.334 

Brake— Dodd 402,966 

Brake— Hogan 447,731 

Brake— Hopper 458,626 

Brake— .James 447,236 

Brake— .James 461,243 

Brake— Lansberg 445,899 

Brake— Marshall 456,199 

Brake— jMassey 451,409 

Brake — Massey 447,783 

Brake— Biggs'! 457.215 

Brake— SUiter. 452.942 

Brake— AVaite 463.085 

Brake— Westinghouse 448,827 

Brake — Westinghouse  et  al..  .461.779 

Brake— Wisuer. 446.908 

Compressor — 14111 448.859 

Compresso]- — Hill 452.132 

Cnmpiessor — Hill 454.590 

Compressor— Hill 463.386 

Compressor — Nordbeig 4.')8.975 

Compressor — Phillips 452.283 

Compressor — Richards 462.776 

Compressor — Riehmann 459.527 

Com]iressor — liiclimann  462.453 

Com]iressor — Sergeant 447.910 

Compressor — Sergeant 456.165 


1892. 

Air  Compressor — Avery 482.775 

Air  Compressor — Beck 476,723 

Air  Compressor — Dillenburg  .  .  .  .481.850 

Air  Compres.sor — Dunn 473.302 

Air  Compressor — Farrell 479,260 


PATENTS. 


809 


Ail- 
Air 

Ail- 
Air 
Air 
Air 

Ail- 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 

Air 
Air 

Air 
Air 
Air 


ivir 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 
Air 


Compressor— Fasoldt 481,527 

Compressor — Guillemet 48-.i,U40 

Compressor — Ifaines 470,tt34 

Compressor — llaiiies 480,193 

Compressor — Ilanford 474,290 

Compressor — llaiistoii  A:  I5ur- 

dan .....471,766 

Brake— Beery 485,365 

Brake— Coali's 467,920 

Brake— Coates 467,921 

Brake— Corporaii 483,802 

Brake— Carpenter 479,736 

Brake— Duval 486,703 

Brake— Dinui 473,302 

Brake— Fahniev 485,182 

Brake— Guillemet 482,040 

Brake— Hannev 476,880 

Brake— Harris'. : 472,190 

Brake— Ilayden 481,651 

Brake— Hoijan 473,839 

Brake— Hogaii 482,058 

Brake— Kiuulsen 468,387 

Brake— McNulta 471,801 

Brake— Marble 484,034 

Brake— Mills 476.546 

Brake— Peltou 482,382 

Brake— Shortt 469,176 

Brake— Sileock 468,701 

Compressor  —  Henderson    & 

Scliultz 475,111 

Compressor — Hutcliinson.  .  .  .581,143 

Compressor — O'Brien 477,381 

Compressor — Perry 485,881 

Compressor — Sliermau 475,251 

Compressor— Teal. 474,034 

1893. 

Eniiine— Durand 497.048 

Eniiue— Field .506,486 

Eugine-Hauserct^Vliittaker.489,148 

Engine- Martin 500,340 

Engine- Muselman 502,860 

Engine— Schou 508,990 

Engine- Smith 491,859 

Compresso!- — De  Laval 511,086 

Compressor — Fogg 493,263 

Compressor — Gustal'son 509,220 

Brake— Barber 494,772 

Brake— Dean 511.071 

Brake— Duval 510,635 

Brake— Duval 510,870 

Brake— Duun 489,527 

Brake— El-body 510,594 

Brake— Hayden 509.898 

Brake— Higgins 503,083 

Brake— Hinckley 508,421 

Brake— Key  wood 500,910 

Brake— Massey 501.016 

Brake — Masterman 504.227 

Brake— Parke  et  al 506,185 

Brake— Pinkston 501,359 

Brake— Pool  et  al 499,582 

Brake— Shallenberger 506,739 

Brake— Sennett  et  al 489,763 

Compressor — Knoche 508,225 


Air  (Jomp lessor— Perry 498,989 

Air  Compressor — Quast 501,046 

Air  Compressor — Sehutzinger. .  ..508,150 
Air  Compressor — Walker 491,233 

1894. 

Air  Engine — Depp 521,762 

Air  Enuine— Rogers 511,969 

Air  Engine— Stewart 519,977 

Air  Compressor — Babcock 523,064 

Air  Compressor — Birner  «fc  Mes- 
sing   520,405 

Air  Compressor — Brotherhood.  .  .515,282 

Air  Compressor — ^Champ 513,556 

Air  Compressor — Champ 515,516 

Air  Compressor — Champ 5-23.830 

Air  Compressoi- — Flood 519,383 

Air  Compressor — Gritlithset  al. .  .530,335 

Air  Brake— Bayley 528,713 

Air  Brake— Browii 520,391 

Air  Brake— Barbridge  et  al 526.178 

Air  Brake— Bishop  .^. 531,584 

Air  Brake— Clark .522,825 

Air  Brake— Clifton 531,100 

Air  Brake— Edwards 527,838 

Air  Brake— Eldridge 537,3'27 

Air  Brake— Fox 530,937 

Air  Brake— Fox 530,938 

Air  Brake— Fox 530,939 

Air  Brake— Haberkorn 531,181 

Air  Brake— Plan-is   515,220 

Air  Brake— Harris 516,203 

Air  Brake— Hunt 529,270 

Air  Brake— James 524,990 

Air  Brake-Jeftries 513,267 

Air  Brake — Knudsen 525,686 

Air  Brake — Lausberg 516,936 

Air  Brake— Lencke 517,955 

Air  Ih-ake— Lencke  et  al.    517,954 

Air  Brake— :MeCarty .529.290 

Air  Brake— liable. ". .5-26,189 

Air  ]5rake— :\[ills .537,784 

Air  Brake— O'Hara 519,681 

Air  Brake— Rothschild 515,616 

Air  Brake— IJothschild 515,617 

Air  Brake — Richardson 513,145 

Air  Brake— Schenck 524,073 

Air  Brake— Schenck 531.137 

Air  Brake— Shortt 530.904 

Air  Brake— Stewart 517,350 

Air  Brake— V^orhees   534,050 

Air  Brake— Vorliees 525,876 

Air  Brake— Willson 516,693 

Air  Compressor — North 527,248 

Air  Comju-essor — Schutz-Heiider- 

sou 517,628 

Air  Comi>ressor — Sergeant 514,839 

Air  Compressor — Sergeant 530,662 

1895. 

Air  Engine — Anderson 537,517 

Air  Engine — Bramwell 543,463 

Air  Engine — Denney 538,068 

Air    Engine — Fletcher    &    Hug- 

irings 547,718 


8io 


COMPRESSED   AIR   AND    ITS   APPLICATIONS. 


Air  Engine — Parsons 549,741 

Air  Eui^ine— Slieniiiui 585,602 

Air  Compressor— Ulakc   584,192 

Air  Compressor — Cliamp 544,450 

Air  Conipressoi' — Cliainp 544,457 

Air  Compressor — Ciiami) 544, 45y 

Air  Compressor — Cliump 544,459 

Air  Compressor — C'liamp 547,768 

Air  Compiessor — Clmquette 548,800 

Air  Comjjressor — Clayton 534,814 

Air  Compressor — Duffy 547.:33S 

Air  Compressor — Dm  and 550,163 

Air  Compressor — Grilliths  et  al.  ..547.882 

Air  Eral<e— Clarke 549,703 

Air  Brake— Conuess 540,539 

Air  Brake — Clirislenseu 534,813 

Air  Brake— Dunn 546,510 

Air  Brake— Frencli 533,286 

Air  Brake — Harris 544,253 

Air  Brake— Harris 547,253 

Air  Brake— Iloii-an 546,448 

Air  Brake— Hoi;aii 546,449 

Air  Brake— Hogan 551.440 

Air  Brake— Hogan 551,767 

Air  Brake— Humbert  et  al 539,430 

Air  Brake— Hunt 545,295 

Air  Brake— Jeffries 550,346 

Air  Brake— Massey 535,844 

Air  Brake— Massey 537,057 

Air  Brake— Schenck 532,914 

Air  Brake— Sennett 53(>,000 

Air  Bi-ak( — Sliortt 538,547 

Air  Brake— Shortt 538,551 

Air  Brake— Sliortt 538,544 

Air  Brake— Shortt 538,549 

Air  Brake—Shortt  et  al 538,546 

Air  Brake— St.eedmau 542,948 

Air  Brake — Tliompsou 545,749 

Air  Brake— Tower  et  al 538.299 

Air  Brake- Trott 536,002 

Air  Brake— Wessels  et  al 548,335 

Air  Brake— Wheeler 546,835 

Air  Brake— White 538,002 

Air  Compressor — Kalthoff 551,549 

Air  Compressor — Keenan 547,519 

Air  Compressor — Lowe  &  Guyser.534,399 

Air  Compressor — Moyer 541,979 

Air  Compressor — Noaek 550,352 

Air  Compressor — Pedrick 544,548 

Air  Compressor — Stambaugh.  . .  .548.399 

Air  C(miprcssor — Taylor 543,410 

Air  Compressor — Taylor 543,411 

Air  Compressor — Taylor 543,412 

1896. 

Air  Engine — Bcrclier 558,475 

Air  Engine — Coon 555,929 

Air  Engine- Good 560,707 

Air  Engine— Good  &  Marichal. .  .558,944 
Air  Engine — Mihsbach   tt   Groe- 

schell 566,785 

Air  Engine — AValling 565,191 

Air  ('ompressor — Champ 570,540 

Air  Compressor — Chaquette 565,429 

Air  Compressor — Clark 558,041 


Air  Compressor — Du  Fanr 561,160 

Air  Compressor— Elliott 568,433 

Air  ('(imi)r('ss()i' — Githens 563,477 

Air  Compressor — (iuyser 560,987 

Air  Brake^ — iJcemer 564, N63 

Air  Bralie— Brookmire 558,670 

Air  Brake— Custer 553,481 

Air  Brake— Custer 553,482 

Air  Brake— Dunn 553,517 

Air  Brake— Dunn 567,024 

Air  Brake— Ferulcy  et  al 553,498 

Air  Brake— Genett 556,815 

Air  Brake— Glass 569,915 

Air  Brake— Graebing 569,823 

Air  Brake— Guillemet 571,115 

Air  Brake— Guillemet 571,116 

Air  Brake— Hall 574,062 

Air  Brake— Harris 571,662 

Air  Brake- Herder 558,174 

Air  Brake— Herbert 572,009 

Air  Brake— High .555,809 

Air  Brake— Howe  et  al 567,476 

Air  Brake— June 570,483 

Air  Brake-Lee .557,511 

Ah-  Brake— Lee 557,512 

Air  Brake— Lee 557,513 

Air  Brake— Lee 557,514 

Air  Brake— Lee 557,515 

Air  Brake— Lindsev 561,596 

Air  Brake— Mable." 572,553 

Air  Brake— Marshall 560,730 

Air  Brake— Noyes 553,565 

Air  Brake— Noyes 564,389 

Air  Brake— Noyes 571,095 

Air  Brake— Noyes 571,786 

Air  Brake— Omick 563,612 

Air  Brake— Park 561,811 

Air  Brake— Rey burn 568,923 

Air  Brake— Bogei-s  et  al 553,294 

Air  Brake— Thompson 571,708 

Air  Brake— Walker  et  al 569,258 

Air  Brake- — Westingliouse 557,464 

Air  Brake— Willets 561,301 

Air  Brake— Zenke 571,736 

Air  Compressor — Hill 571,971 

Air  Compressor — Tjiming 569,929 

Air  Compressor — ]\Ier]'itt 562,475 

Air  Compressoi'— Niehols 555,178 

Air  Compressor — Noyes 563,794 

Air  Compressoi- — Pendleton 561,126 

Air  Compressor — Re.ynolds 572,377 

Air  Compressor— Roberts 572,314 

Air  Compressor — Sergeant 568,804 

Air  Compressor — Shaw 552,590 

Air  Compressor — Smith 572,383 

Air  Compressor — Underwood. . .  .558,135 

1897. 

Motor  Car— R.  Hardie 584,146 

Air  Compressor— I.  T.  Dyer 585,090 

Pneumatic  Despatch — B.  C.  Bach- 

eller 585,498 

Air  Spray- John  Black 585,503 

Air  Brake— E.  A.  Trapp 585,927 


PATENTS. 


8ll 


Compressor     and     Cooler — John 

Flindall 585 

Air  Compressor — W.  H.  Knight.. 586 

Air  Motor— J.  H.  Hoadley 586 

Pneumatic    Sole — Julia    F.    Bas- 

com 586 

Air     Compressor — Alfred     Shed- 
lock 586: 

Pneumatic     Press — P.    C.    Blais- 

dell ns6 

Air  Compressor — I.  H.  Spencer.  .5SS 
Hot- Air  Motor— W.  Trewliclla.  ..588 
Air  Compressor — E.  (!.  Nichols..  589 

Water  Elevator— John  Hass 588 

Pneumatic  Convej'or — A.  P.  Hes- 

lop 588 

Valve— James  Clavton 587 

Air  l^unp— II.  S.  Bills 587 

Kailwav  Switch — Johnson  &  ISlc- 

Keithen 590 

Strav^r  Stacker- L.  I).  Parmley.  ..589 
Pneumatic  Motive  Powei' — L.  II. 

Meyer 590 

Pneumatic  Tool— F.  E.  Hartham .  590 
Air    or    Gas    Compressor — S.    S. 

Miles 591 

Pneumatic  Drill — J.  II.  j\Ianning.591 
Pnemnatic  Motor— G.  W.  Smit]i..591 
Water-Elevator— P.  S.  A.  Bi('kel.591 
Pneumatic  Hanuner — C.  II.  John- 
son  592 

Air  Compressor — E.  Hill 598 

Pneumatic  Painting  Apparatus — 

A.  FLsher 593 

Pneumatic  Water-Raising  Device 

— E.  Pitcher ' 593 

Pneumatic  Motor — F.  W.  Hedge- 
land 593 

Pneumatic  Motor — T.  P.  Brown. .594 
A  i  r-C  o  n  t  r  o  1 1  i  n  g    Device — A. 

Roesch 595 

Pneumatic    Conveyor— S.    H. 

Jones 596 

Dry  Kiln— Franklin  Kirk 596 

Pneumatic  Stacker — G.W.Quinn.596 
Drying    Ajiparatus — MeClatcliev 

&  Krum ■  596 

Pneumatic  Despatch  Tube — C.  F. 

PiUe 595 

Air  Pump  or  Compressor — L.  B. 

Alberger    595 

Air  Engine— Anderson  &  Ericks- 

son 579 

Air  Engine — Barbour  &  Hansen.  .591 

Air  Engine — Berry 583 

Air  Engine— Bole 592 

Air  Engine— Gibbs 592 

Air  Engine — Goth 580 

Air  Engine — Parke 594, 

Air  Engine — ^Roediger 579 

Air  Engine — Weimer 577 

Air  Compressor — Crabtree 594 

Air  Compressor — Griffiths  et  al. .  .576 

Air  Brake— Boyden 583 

Air  Brake — Boyden 583 


Air  Brake-Buckpitt. 589,957 

955      Air  Brake— Bragg  et  al 593,531 

100      Air  Brake— Bentley 574,656 

137       Air  Brake— Conness 587,519 

Air  Brake — Con-ingtou 594,464 

155      Air  Brake— Dunn. 577,435 

Air  Brake— Fish 5!»3,!)!t6 

669  Air  Brake— Gunckel 5S2,  :!!M 

Air  Brake — Ilogan 574,^66 

946       Air  Brake— Hunt 581,913 

396       Air  Brake— Mcintosh 589,3()5 

509       Air  Brake— Nellis  et  al 594,083 

190      Air  Brake— Omick 58S,918 

825      Air  Brake— Redfeiu 5.S4,705 

Air  Brake — Shearwood 574.498 

908      Air  Brake— Shortridge 57S,  168 

704      Air  Brake— Westinghouse  et  al. . .  593,461 
638       Air  Brake— Winters 594,228 

Air  Compressor — Peiiue   580,714 

153       Air  Compressor — Sergeant 579,775 

853      Air  Comi)ressor — Toennes 576,920 

Air  or  Gas  Compi'essor — I.  (!rab- 

686  tree 594,524 

661 

1898. 

137       Air  Lift  Pump— ^V.  L.  Saunders. 567,023 
284       Compi-e.ssed  -  Air     Ap])aratus — J. 

018  ]\lelntyre 596,822 

029       Drier— K.  *S.  P.liuichard    596,470 

Grain  Drier— W.  E.  Ellis 596,655 

116       Refrigerator— J.  II.  Barrett 596,967 

049       Air  Compressor— T.  H.  Roberts.. 597, 333 

Lmnber  Drier— H.  J.  JMorton. . .  .597,548 
013       Air  Valve— S.  C.  Aiiiold 597,666 

Air  Brake— H.  F.  Noyes 599,348 

431       Air  Compressor— J.  H.  Hoadley.. 598, 149 

Governor    Valve,    Compressor — 

655  Christensen 598,383 

891       Pneumatic  Spring— W.  Ko\valelT.598,103 

Air  Disc-Brake— ]\I.  E.  Campany  .598,766 
654      Air   Cleaning,  Cooling   Device — 

McCreery '. 599,080 

311       Pneumatic  Conveyor — S.   C.   Da- 

313  vidson 599,055 

307       Pneumatic  Sprini-— E.  E.  Egger. 598,982 

Pneumatic  Stacker— G.W.Wood. 599,379 
175       Street-Car  Air  Brake— C.  xV.  Gray .  599, 42 1 

Drier— A.  S.  Liveugood 599,509 

890       Fruit  Drier — Steevens  &  Steevens 

599,647 
439       Air  Brake— Xoyes 599,349 

Air  ('ompressor — P.  Cramer  . .  .  .600,358 

670  Air  C^ompressor  (re-issue) — F.   ]\[. 

584  Graham 11,654 

357  Comjiressor — J.  Stumjif 600,636 

688  Hot-Air   Compressor  —  Anderson 

246  ct  Ericksson 601,031 

600  Air  Brake— W.  O.  Gunckel 601 ,353 

901  Air-Brake  Valve— W.O. Gunckel  .601,352 

654  Pneumatic    Hub — W.    C.    Kone- 

.568  man   599,907 

534  Liquid  Distribution — F.  31.  Gris- 

864  Avoid 599,702 

278  Air  Brake— Catlett 598,814 

379  Air  Brake— Gunckel 601,353 


Sl2 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Air  Brake— Hamar  ct  al 600.641 

Air  Brake — Kholodowskl (j()0,r)87 

Air  Brake— Olin nDS.GTS 

Air  Brak( — Perkins 59S,,S87 

Air  Brake— Petteuuell 597,220 

Air  Brake— Wands 604,244 

Air  Compressoi— H.  C.  8ergeaut.602,y77 
Conii)resse(l-Air      II  a  ni  ni  c  r^ — J. 

Schmidt 602,198 

Valve,  Air  Compressor — F.  Ricli- 

ards 602,473 

Hydraulic  Air  Pump — E.  II. 

AVeatlieriiead 603,242 

II 3'  d  r  a  u  1  i  c   Air  C  ompressor — 

W.  F.  Stark  602,247 

Air  Brake— J.  J.  Kef 602,094 

Air  Valve— E,  A.  Rix 602,170 

Hot-Air  Furnace- J.  T.  Warren.. 601, 822 

Air  Distributor— J.  Jaucli 603,105 

Pneumatic    Despatch    Tube — H. 

Clay 603,174 

Pneumatic  Organ— M.  Clark 603,127 

Governor     Air     Compressor — C. 

Cummings 603,425 

Pneumatic  Elevator— J.  B.  Sehu- 

man 603,925 

Pneumatic  Despateli— Mat  bias.  ..604,405 

Air  Brake-W.  O.  Gunckel 004, ()12 

Compressed    Air   Engine— L.    T. 

Gibbs 604,745 

Air   Compressor — O.     II.     Briiig- 

ham 604,717 

Air  Compressor— E.  Bottini 604,962 

Air  Brake— W.  H.  Clowrv 605,394 

Hot-Air  Furnace— T.  G.  Keal.  ..  .605,829 

Air  Brake- II.  S.  Park 605,904 

Air  Brake— II.  S.  Park 605,905 

Pneumatic  3Iotor — F.  W.  Hedge- 
land r.  .605,876 

Air  Compressor— F.  Richards.  . .  .606,428 
H  y  d  r  a  u  1  i  c   Air  Comiiressor— 

Noack 606,732 

Hydraulic    Air   Compressor^ 

iSToack 606,733 

Air  Brake— William  Hirst 607,371 

Air  Brake— :\I.  Carrington 606,708 

Air  Brake— L.  F.  Guillemet 606,712 

Hot-Air  Furnace — H.  L.  Win- 

gert 606,752 

Valve-Gear,  Air  Compressor — Se- 

derholm 607,195 

Hot-Air  Furnace— J.  T.  ct  J.  K. 

Brien 607,793 

Gas  Power  Process — E.  N.  Dick- 

erson 607,655 

Air  Brake— C.  L.  Ansley 608,095 

Air  Brake— :\Iurrav  CJorrinijton.  .608,030 
Air  Compressor— C.  N.  Dutton.  .609,087 
Air  Compressor- C.  X.  Dutton.  .009,088 
Air  Compressor — Heston  ct  Ilar- 

vison 608,964 

Air  Brake— F.  L.  Guillemet 608,599 

Air  Brake— F.  L.  Guillemet 608.600 

Air  Brake— H.  S.  Parke 608.621 

Air-Brake— J.  J.  Nef 609.041 


Air  Brake— J.  J.  Nef 609,042 

Pneumatic  Despatch  Tube— S.  R. 

Gayton 610,528 

Air-Compressor     Inlet-Valve— J. 

G.  I.eyner 610,608 

Tide-"\Vatcr     Air     Compressor — 

Beckers 610,790 

Pneumatic  Motor — F.  W.  Hedge- 
land 611,629 

Locomotive    Air    Brake — W.    P. 

Alter 612,149 

Automatic  Air  Brake — McLaugh- 

Hn 612,778 

Air  Brake— W.  T.  Hamar 613,143 

Air    Compressor    Governor — 

Libby 013,692 

Air  Agitator— E.  F.  Porter 614,275 

Air  Engine— M.  Schmidt 614,992 

Air  Brake— J.  F.  Voorliees 615,326 

Pneumatic  Dry  Dock — C.  N.  Dut- 
ton  615,440 

Air  Compressor — W.  H.  Barr.  . .  .615,668 
P  n  e  u  m  a  t  i  c    Gas    Lighter — E. 

Knapp .^ 615,717 

Air  Brake— 31.  Corrington 616,288 

1899. 

Hydraulic  Air  Compressor — Ster- 

zing 618,243 

Hydraulic  Air  Compressor — Tay- 
lor  ;. 618,243 

Air  Brake— E.  A.  Hauerwas 618,204 

Air  Purifier— AV.  S.  Whitney. . .  .616,997 

Air  Moistener— W.  H.  Prinz 618,615 

Air     C  om  p  r  e  s  s  o  r — Lowell     & 

Brown 618,959 

Air  Brake— R.  E.  Wynn 619,381 

Air  Heater— J.  Hitctriubottcmi.  ..  .619,483 

Air,  Gas  Engine— Eisenliuth 620,554 

Air  Brake— Ansley  ct  Topham. .  .621,779 
Liquefying      Air — Ostergren     ct 

Burger 621,536 

Liquefying     Gas — Ostergren     ct 

Burger 621,537 

Air  Compressor — H.  E.  Anderson. 620, 833 
Aerating  Water  in  Bottles— H.  V. 

R.  Reed 620,963 

Air  Valve— J.  H.  K.  McCollum.  .621,841 
Air-Supplviug  Apparatus — F.  A. 

Baynes 620,830 

Air  Brake   Safety  Attachment — 

A.  C.  Rumble 624,103 

Air  Compressor— F.  W.  Ensign.. 624, 002 
Pneumatic  Despatch — E.  A.  For- 

dyce 624,201 

Pneumatic    Carrier — E.    A.    For- 

dyce 624,203 

Pneumatic    D  e  s  p  a  t  c  h — B.     C. 

Batcheller 623,970 

Pneumatic     Despatch — B.    C. 

Batcheller 623,971 

Carrier— B.  C.  Batcheller 623,973 

Carrier  Receiver— B.   C.  Batchel- 
ler  623,973 


PATENTS, 


«I3 


Pnt'Uiiiatic  Tmnsmission — Ijutch- 

elliT ()'2:5,9G8 

Pucunialic  Trausinissioii — IJatcli 

filer r)t3:5.9r)0 

Air  Compressor — A.  Roescii (i24,0l)9 

Hydraulic     Air     Compressor — J. 

Limiim- ()24,S:30 

Gas  Engine- \V.  II.  ^'  J.  Butiei- 

worth (J24,T."")0 

Compound      Air      Comjiressor — 

WuUick ()-24.998 

Valve  for  Air  ^Motors — I.  Craig, 

Jr '.  .r,2.-).824 

Red\K'iug  Valve — I.  Craig,  Jr...  .(52.-),3'3."j 
Liquefying    Gases — J.    E.    John- 
son   G27,(i96 

Air  Compressor  and   Cooler— R. 

Berg (526,883 

Pneumatic     Dispatch     Cai'rier — 

Fordvce   627,181 

Pneumatic  Organ— 31.  Clark 626,320 

Com]iression     Controller — F.     G. 

Ilobart 62r,8r)0 

Air  Cooler— J.  ]\LcCreerv 626,390 

Atomizer— R.  Morrill,  ." 628,251 

P  n  e  u  m  a  t  i  c   Carpet-Sweeper — 

Wcstman 628.. m") 

Water  Elevator— F.  Hayes 628,318 

Air-Brake      Hose     Coupling — J. 

Caldwell :...  .629,657 

Air  Brake— E.  Bartholomew 629,708 

Trii)le  Valve  for  Air  Brakes— W. 

B.  :\rann 630,379 

Engine   for   Air  Piimiis — W.    B. 

'^^[ann   630,380 

Air  Brakes— AV.  B.  3Iann 630,381 

Air  Compressor — R.  L.  Dunn.  ..  .630,495 
Air  Compressor — C.  O.  Sobinski..630,525 
Pneumatic  Prt)pu]sion— Walker .  .630,821 

Air  Omtroller— S.  H.  Short 630,938 

Air  Cooler— J.  AIcGreery   631,377 

Pneumatic  Hammer — C.  K.  Pick- 
les  631,435 

Air  Compressor — C.  F.  DuBois.  .631,701 
Compressed    Air    Pump — T.    C. 

Wristen 631,732 

Air  Puri tier— Fowler  &  Harpole..631,868 
Air  Compressor — P.  H.  ^Montague  .631,994 

Air  Drill— A.  P.  Schmucker 633,661 

Pneumatic  Organ— M.  Clark 632,698 

Pneumatic  Despatch— Batcheller. 632, 690 
Pneumatic  Signal  for  Trains — C. 

Guiland 632.813 

Track-Sanding      Device — J.      H. 

Handon.'. ...633,193 

Track  Sanding  Apparatus — J.  H. 

Handon 683,194 

Valve  for   Pneumatic    Tools— J. 

Boyer 633,355 

Valve     Controller— Schoelf  el     Sc 

Aylward ...632,207 

Combustion  Motor — R.  ]\rewes.  .  .633,878 
P  n  e  u  m  a  t  i  c    Pipe    O  r  g  a  u — 

Schmelzeis 633.735 

Pneumatic  Insole — A.  Korwan.  ..632,529 


Pneumatic    Carpet    Renovator — 

Thurman 634,042 

Air  Feetler  for  Furnaces — J.  How- 
den 634,3-18 

Air  Compressor — P.  Brotherhood. 634, 389 

Air  Brake — C.  X.  Dutton. 634,723 

Ail'  ComiHcssor — S.  Broichgans.. 635,419 
Pneumatic  Despatch — Fordyce .  .635,434 
Hydrauli('      Air     Pump — llaber- 

mann 635,478 

Air  Comjiressor — J.  P.  Sinunons. 635,516 
Air  Compressor — J.  P.  Simmons. 635,517 

Air  Valve— W.  J.  Cole 635.661 

Portable  Air  Pump— A.  B.  Diss.. 635,674 
Automatic  Air  Brake— Clarke. .  ..635,095 
Air  Compressor— G.  W.  Tolle  .  .  .636,013 
Air  Heater— Waterman   &  3Iori- 

son 636,090 

Air     Purifving      Apparatus— E. 

Gates.! 636.256 

Sand  Blast— J.  :M.  Xewhouse 636,279 

Tire  Intlater— J.  F.  Wilson 636,308 

PneuniaticValve — H.Leineweber.636,343 
Cotton-seed    C  o  u  v  e  v  o  r — J.   T. 

.Moore " 636,414 

Cow-Milker— X.  II.  Xorhy 636,446 

('ompressor.     Ice    M  a  c  ii  i  n  e  s — 

Sharpncck 636,459 

SandBlast  Machine— G,   S.   Slo- 

cum 636,460 

Air  Compressor— S.  A.  Donnelly  .636.643 

Air  Puritler— J.  C.  Fleming 636,651 

Cotton-Handler— D.  C.  Joiies. ..  .636,670 

Time  Valve— F.  L,  Dodgscm 636,770 

Air-Brake  Hose-Coupling— Park- 
inson  ' 637,021 

Pneumatic   Rocker — Ander.son  c*c 

Anderson 637,065 

Hvdraulic  Air  Compressor — L.  E. 

Mitchell 637,144 

Pump    for    Compres.sing   Air  or 

Gas— H.  E.  Ludwig 637,516 

Air  C(nnpiTssion — Pettee  6c  Mc- 

Cutchan    637,659 

Air  Alotor— Pettee  &  McCutchan. 637,660 
Air  Compression — Pettee  ct   ]\Ic- 

Cntchan 637,661 

Air  Supplier  for  Diving — F.    A. 

Hensley ' 638,392 

Pneumatic  Despatch — C.  F.   Bo- 

dinus 638.409 

Air  Compressor — J.  H.  IIopps.  .  .638,460 
Pneiuiiatic    Ram — A.    L.     Hum- 
phrey  638,928 

Air  Pyrometer — I'ehling  lV  Stein- 

bart ! 639,317 

Mercurial  Air  Pumj) — H.  S.  Max- 
im  639,593 

1900. 

Air  Pro]U'ller— A.  Duffncr,  Jr. .  ..640,184 

Air  Drier— A.  T.  Perkins 640,318 

Air  Drier— A.  T.  Perkins 640.320 

Pneumatic  Tube— S.  F.  Jones.  ...640.386 


8i4 


COMPRESSED    AIR   AND    ITS   APPLICATIONS. 


Air  and  Gas  Engine — F.  AV.  Eisen- 

hutli 640,890 

Air  Ejector — G.  Quanonne   040,946 

Air-Conipressiug   Engine— E.   A. 

Kix ^ 640,949 

Air  Pump— C.  E.  8eril)ner 641,409 

Pneumatic  Despatcli  Tube — C.  A. 

Gray 641,384 

Air-Lock  Caisson — K.  S.  Gillesi)ie.641,50o 
Air  Compressor — AV.  I).  Hooker.. 643, 185 

Relieater— T.  A.  Edison 643,764 

Hydraulic  Air  Compressor — How- 
ard  643,962 

3Iarine    Air    Compressor — J.    P. 

Place 644,093 

Electric  Controller — Christeusen..644,128 
Liquid  Air  Storage — Ostergren  .  .644,2.')9 

Air  Meter— S.  L.  Teriy 644,840 

Pneumatic  Abater  Supply — Kins- 
man  ■ 644,711 

Pneumatic  Separator— C.H.  Lane.  645, 962 

Air  Compressor — AIcKinnon 646,030 

Air  Compressor — AIcKinnon 646.081 

Air-Pipe  Coupling — Spurlock.  ...646.240 
Compressed-Air     ]\Iotor — B.     P. 

Kvder 646.318 

Pneumatic  Hoist— H.  A.  Pedrick. 646.458 
Liquid- Air  Vessel— J.  F.  Place.  ..646,459 
Air  Lift  Pump— G.  H.  Evans.  ..  .646,640 

Sand  Blast— W.  H.  King 646.740 

Air  Belt-Shipper- J.  Woodberry  .646,892 
Pneumatic  Spring — J.  C.  Ander- 
son  647,246 

Liquid-Air  Bottle— H.  Karrodi.  ..647,002 

Pneumatic  Drill— J.  A.  Hoff 647,265 

Pneumatic  Tool— J.  Keller 647,415 

Pneumatic  Rammer — J.  Keller.  ..647,416 
Pneumatic  Drill— E.  C.  Meissner. 647,455 
Liquefaction  of  Air — O.  P.  Oster- 
gren  647,514 

Pneumatic  Carrier — B.  C.  Batch 

eller 648,375 

Air  Refrigerating— J.  D.  Aloran  .648,422 
Locomotive  Track-Sander — C.  A. 

Pratte 648,709 

Pneumatic  Despatcli  Carrier — J. 

T.  Cowlev 648,853 

Signal— J.  H."  AFcCarthy 649,523 

Heater  for  Air  jNIotors — J.  Craig, 

Jr 650,525 

P  n  e  11  m  a  t  i  c    Propeller — J.    P. 

Hickey 650,535 

E.xplosive  Liquid-Air  Engine — J. 

C.  Anderson T 651,741 

Dry-Air  Apparatus — J.  Gavlev.  652,178 
Air-Drying  Process- J.  Gay  ley.  .652,179 
Pneumatic  Tube — W.  A.  Hough- 

talincr 652,270 

Air  Cooler— J.  McCreeiy 652,463 

Pneumatic  Store  Service — H.  W. 

Forslund 652,537 

Air  Pump— C.  M.  Hobliy 652,559 

Air  Compressor — H.  C.  Sergeant. 647,883 
Pneumatic    Convever — M.    J. 

Foyer ". 652,960 


Air-Hoist— G.  F.  Steedman 652,983 

Switch,  Pneumatic  Carrier — Tai- 

sey 653,044 

Hvdraulic    Air    Compressor — D. 

Kirkman 653,094 

Air  Compressor — Bowker&  Sher- 
man  654,511 

Pneumatic  Despatch   Tube — W. 

Townsend 654,690 

Pneumatic    Water-Elevator — 

Shauffleberger 654,764 

Air  Purifier- R.  H.  Thomas 655,285 

Air  Power — A.  M.  Becker 655,541 

Air     Brake,     Automobile — Ham- 
mond   655,654 

Air-Pipe  Coupling — J.  W.  Spur- 
lock  ". 655,997 

H  y  fl  r  a  u  1  i  c    Compressor — Van 

Brocklin 656,147 

Air  Brake- F.  L.  Clark 656,516 

Water-Raising      Apparatus — Pe- 

termann 656,572 

Air     or     Gas     Engine  —  R.     H. 

Little 7. 656,823 

Air  Compressor — E.  Hum 657,025 

Pneumatic  Tube  Carrier — Batch- 

eller 657,076 

Pneumatic  Tube  Carrier — Batcli- 

eller 657,077 

Pneumatic  Tube  Carrier — Batch- 

eller 657,079 

Pneumatic  Despatch  Tube — Cow- 
ley  657,090 

Pneumatic  Despatch  Tube — Cow- 
ley  657,091 

Pneumatic  Despatch  Tube — Cow- 
ley  657,093 

Pneumatic  Gun — E.  M.  Gold- 
smith  657,344 

Pneumatic  Riveter — H.H.Prange.657,449 

Air  Brake— J.  J.  Nef 657,669 

Air- Actuated  Pump— Bartell 657,758 

Compressed  -  Air       Carburator — 

Bouvier 657,755 

Air  Compressor — Emile  Gobbe.  ..657,868 
Pneumatic    Despatch   Tube- 

Pearsall 657,886 

Reheater— T.  A.  Edison 657,922 

Pneumatic    Despatch — Bavier  & 

Hawkes 658,103 

Pneumatic    Despatch — Bavier  & 

Hawkes 658,103 

Pneumatic  Steering — C.  Jauczar- 

ski 658.265 

Liquid  Air— O.  P.  Ostergren 658,322 

Pneumatic  Hammer — E.  A.  For- 

dvce 658,542 

Liquid- Air  Lift-.T.  Clavton 658,941 

Pneumatic  Or<ran— M.  Clark. . .  .659,210 

Air  Ship— C.  Stanley 659,264 

Hydraulic  Air  Compressor — Web- 
ber  659,270 

Pneumatic  Hammer — C.  K.  Pick- 
les  659,418 

Liquid-Air  Lift— J.  Price 659,491 


PATENTS. 


815 


Recording  Air  Pyrometer — Bris- 
tol  659,616 

Pneumatic  Type-Writer — M.  So- 

blik 659,703 

Air  Extractor — Ellingwood 659,730 

Pneumatic    Cottou-Picker  —  Me- 

vers 659,752 

Air   Pump   and   Compressor — G. 

8ipp 659,832 

Air  Rifle— W.  J.  BurroAV 660,070 

Pneumatic  Stacker — Hi x  son  & 

Tarrant 660,159 

Air  Compressor — J.  Keith 660,253 

Air  Mattress— A.  H.  Sawtell ()60,466 

Air  Brake— J.  E.  Normaud 6()0,650 

Pneumatic  Tool — H.  J.  Kimman  .660,705 
Compoiuid  Compressor — T.  Grant660,793 
Pneumatic  Tool— H.  G.  Kotten.  .660,857 
Air-Gas  Apparatu.s— C.  W.  Miller. 660,916 

Air-Lift  Pump— T.  Butler 660,946 

Pneumatic     Hammer^Jones     & 

Pierce 660,961 

Air  Cooler— J.  T.  Nicholson 660,997 

Air  Brake — J.  R.  Richardson. .  .  .661,075 

Air  Brake— J.  Shourek 661,111 

Ammonia  Compressor — Ludlow .  .661,184 
Air-Brake  Valve — -Krinimelbein.  .661,474 

Air  Brake— D.  Becmer 661,572 

Air-Brake     Release    Valve — Cor- 

bett 661,574 

Air  Brake— W.  K.  Omick 661,584 

Air-Lift  Pump— C.  Shaw 661,624 

Air  Brake— J.  J.  Nef 661,702 

Air  Propeller— New-marker 661,724 

Air-Lift  Pump— C.  Shaw 661,623 

Pneumatic  Hammer— Beckwith. .661,786 

Air  Motor— R.  A.  Gaily 661,860 

Air  Furnace— B.  A.  Brown 661,950 

Repeating  Air  Rifle — W.  J.  Bur- 

"  row .  .662,054 

Petroleum     Burner — Charon     ik 

Manaut 662,055 

Air  Vent— A.  Roeseh 662,093 

Air  Brake— W.  K.  Omick 662,152 

Compressed-Air      Engine  —  M. 

Flood 662,189 

Pneumatic  Tire  and  Shoe — Vree- 

land 662,208 

Water-Ballast  Controller— G.  B. 

Wilcox 662,830 

Air  Conveyer— E.  L.  McGary 662,574 

Pneumatic  Carrier — Pearsall 662,601 

Pneumatic  Tool — Leineweber.  ...662,675 
Pneumatic   V"alve-Action — C.  M. 

Welte 662,705 

Pneumatic   Cash   Carrier — F.    C. 

Cutting 662,771 

Pneumatic    Lubricator — Vandre- 

sar  &  Pilling 662,838 

Hydraulic     Air      Compressor  — 

Starke -...662,884 

Pneumatic     Hammer — D.    S. 

Waugh 662,993 

Pneumatic  Tire— E.  Arthur 663,001 

Air-Brake  Coupling — B.  Vaughn. 663, 110 


Pneumatic  Piano- Action— J.   W. 

Crooks 663,118 

Pneumatic    Straw-Stacker — Con- 
ner  663.150 

Air-Brake  Chart— Lofy  »&IIinger.  663, 236 

Air  Compressor — J.  Keith 663,500 

Pneumatic  Tire— F.  H.  Mason.  ,  .663,633 
Pneumatic   Refrigerator — Cole  & 

Cole 663,731 

Air  (Compressor — N.  A.  Christen- 

sen 663,862 

Air-Compressor  Regulator — Hew- 
lett  664,086 

Pneumatic    Track-Sander— J.    B. 

Barnes 664,115 

Aerating  Liquids— W.  Hill 664,150 

Pneumatic  Cushion  Post — J.  W. 

StoU 664,184 

Air  Compressor— IL  M.  Salyer.  ..664,230 
Pneumatic  Spring  or  Cushion — 

S.  H.  Stubbs 664,444 

Pneumatic  Despatch — J.  M.  Hes- 

tor 664,547 

Unloading   Device — de  Laval   & 

Aborn 664,562 

Unloading   Device — de   Laval   & 

Aborn 664,563 

Pneumatic     Riveter — Tynan     »fc 

Mostiller 664,596 

Air  for  Furnaces — .1.  Vicars.  .  .    .664,695 

Air  Valve— T.  Wheatley 664,699 

Liquid  Agitator — R.  Conrader. .  .664,723 
Pneumatic  Tire— A.  H.  Lewis. .  .664,766 

Air  Agitator— E.  F.  Porter 664,776 

Pneumatic  Butler— F.  A.  Mills.  .664,816 
Air  Fluid-Lift— G.  Schmidt 664,824 

1901. 

Pneumatic  Tool— C.  B.  Richards. 665, 033 
Pneumatic  Tool— .T.  S.  Stevenson. 665,281 
Pneumatic     Oil-Pump  —  G.     W. 

Turner 665,285 

Pneumatic    Hammer   Casing — 

Chapman '^ .  .665,391 

Air-Cooling  Device — S.  B.  Waters 

665,392 
Air  Compres.sor— .T.  G.  Lapham..665,448 
Pneumatic    Hammer — J.    Beche, 

Jr 665,564 

Train-Signalling        Apparatus — 

Harris 665,852 

Rotary  Air-Pump— J.  Aitken 666,588 

Pneumatic  Organ  Action — Flem- 
ing  666,658 

Air-Pressure  Hoist — Christensen  .665,993 
Air  ^V^ater-Elevator— H.  L.  Frost. 666. 659 
Pneumatic  Eniiine- C.K.  Pickles. 666, 690 
Liquid- Air  Cooler— J.  F.  Place. .  .666,692 
Liquid-Air  Cooler— J.  F.  Place.  .666.693 

Pneumatic  Carrier — Fordyce 666.747 

Air  Hammer— C.  H.  Johnson 666,757 

Air  Motor— H.  L.  Arnold 666,840 

Pneumatic  Trolley— J.  B.  Linn.  .667,133 
Pneumatic  Despatch— C.  H.  Bur- 
ton  667,185 


8i6 


COMPRESSED    AIR    AND    ITS   Al'PLICATIONS. 


Piiciiniatic   Tube  -  Service — Furs- 

liiiul 667,20'J 

Air  Pump-G.  W.  Kellogg 667,224 

Pneumatic  ]Miilting  Apparatus — 

F.  Knuttel 667,229 

Pneumatic     Straw-Stacker  —  Kit- 

tleson 667,322 

Pneumatic  Painting  Apparatus — 

Redman 667.369 

Pneumatic    Arrow — Krat/Bous- 

sac 667,630 

P  n  e  u  m  a  t  i  c  Straw-Stacker — T. 

Goodale 667,694 

Pneumatic     Hammer — J.    K. 

Lencke 667,784 

Pneumatic  Hanuner— J.  Boycr.  ..667,863 
Pneumatic  Locomotive  Sander — • 

Xeufter 667,948 

Air  Brake— R.  B.  Benjamin 668,152 

Pneumatic  Impact  Tool— Oldham  668,354 

Air  Ship— A.  F.  Iluljljard 668,375 

Pneumatic  Tire— J.  Adair 6<)8.39s 

Pneumatic  Pump— D.  L.  Ilolden. 668.405 

Air  Brake — Christensen 668,  (i  13 

Pneumatic  Tire— P.  S.  Gritlith. .  .668,733 
Compressor-Lubricator — ]\Iichalk  669,065 

Pneumatic  Drill— J.  Boyer 669,069 

Air  Compressor — F.  J.  A.  Kinder- 

mann 669,118 

Gas  Compressor — W.  Knapp. ..  .669,140 

Air  Valve— R.  L.  Ambrose   669,316 

Pneumatic  Despatch— Pearsall.  ..669,485 
Pneumatic      Stiaw-St  acker — An 

drews 669,500 

Pneumatic  Tool— W.  11.  Solev.  ..670,645 
Pneumatic  Tool— W.  11.  Soley.  ..670,646 
Air  BelioAvs— T.  P.  lirown.  .'  . .  .670,700 

Rock  Drill— Warren  AVood   670,750 

Air-Gun— F.  F.  Bennett 670,760 

Air-Ship-0.  Olsen 670,807 

Air  Compressor— G.  B.  Petsche.. 670,810 
Pneumatic  Tire— P.  W.  Tilling- 

hast 670,866 

Air  Brake— F.  Lince 670,901 

Pneumatic  Hammer — C.  H.  Shaw. 669. 599 
Pneumatic  Tire— B.  Wakemau. .  .669.606 
Air  Compressor— G.  B.  Petsche.  .669.853 
Tubular  Transmission — Bogardus 

669.888 
Pneumatic  Transmission — Bosrar- 

dus 669,889 

Tubular  Despatch— Bogard  us ... .  669. 890 
Tubidar  Transmission — Bogaidus 

669,891 
Tubular  Despatch— Bogardus.  ...669,892 
Hj'di'aulic  Air  Compressor — Lin- 
ton  669.995 

Air  Compressor— F.  H.  :\Ierrill.  ..670,000 

Air  (Compressor — C.  Garver 670,153 

Air  Brake— W.  S.  Palmer 670,245 

Pneumatic  Hul)- T.  Coad 670.310 

Air  Pump— J.  B.  Hilliard 670.399 

Pneumatic  Tire— Tillinghast.  . .  .670,412 
Air-Brake   Check  Valve— W.    S. 

Morris 670,563 


Air  Compressor— G.  S.  Bincklev.671,044 
Air  Brake— A.  Cowperthwait .  ".  .671,207 
Comprcsscd-Air    Pumj) — R.    W. 

Elliott 671,209 

Pneumatic    Actuator— Schwcsin- 

ger 671.289 

Air-Pump  Governor — Stewart.  .  .671,244 
Ventilation,     Tunnel — C.    S. 

Churchill 671,264 

Pneumatic  Tire— A.  II.  Beck 671,365 

Air-Lift  Pump— J.  E.  Bacon.  ..  .671,428 
Pneumatic  Tin — Bryan -Hay  mes.  671, 535 
P  u  e  u  m  a  t  i  c    Power-Cy  liuder — 

Lindstrom 671,559 

Liquefied-Air  :Motor— Osterirren..671,608 

Rock  Drill— H.  Koch ^ 671,970 

Pneumatic  Tire— B.  WaUeman.  ..671,986 
Pneumatic     Package-Holder — G. 

H.  Wall 671,987 

Pneumatic  Tire— H.  L.  Warner.  .672,073 

Hock-Drill- L.  T.  Sicka 672,082 

Rock-Drill— L.  T.  Sicka 672,083 

Air  Barke— G.  Westingliouse. . .  .672,115 
Pneumatic-Tire    Valve     Tool — 

Xoves 672,217 

Portable  Pneumatic  Drill— Dean. 672,263 
Pneumatic  Tov— J.  L.  3Iaull.  . .  .672.277 
Pneumatic  Tool— T.  Barrow.  . .  .672,306 
Pneumatic   G  rain-Carrier — Schei- 

degger 672,409 

Pneumatic  Hammer — J.  Dunlop..672,638 
Pneumatic    Straw -Stacker — Con- 
ner  672,732 

Pneumatic  Malt  System— Renner.672,843 
Pneumatic  Despatch — R.  T.  Jen 

ney 672,905 

Rotary   Motor   or   Pump — West- 

iii  "house 672,970 

Rotary  Pu  m  p— G.  Westinghouse. 672, 971 
Pncum.atic   Spring — W.    W.   An- 

nable 673,011 

Pneumatic  Tire— J.  Hubbard 673,055 

Pneumatic   Shoe-Form — Ruggles 

&  Wiesen 673.068 

Valved  Piston— J.  P.  Simmons.  ..673.068 

Liquid-Air  Holder — Bobrick 673.073 

Rock  Drill— W.  Wood 673.104 

Pi'essure-Regulator — Bullock.  . .  .673.133 

Air  Valve,  Radiator— F.  :\Iorgan.6T3.217 
Air  Valve— W.  H.  Duer.  . .   ...  .673.319 

Riveting-Tools  Supporter — Mull  .673.407 
Riveting-Tools  Supporter — ]\Iull. 673.408 

Riveting  Apparatus — 3Iull 673,444 

Riveting  Apparatus — 3Iull 673,445 

Air-Brake  Coupling —J.  H.  Phil- 
lips  '. 673,566 

Pneumatic  Spring, Vehicle — Hum- 
phries  673,682 

Pneumatic     Despatch     Carrier — 

Pearsall 673,725 

Liquid- Air      Apparatus — Hatha- 
way  ..673,774 

Compressed-Air  Carriage — Conti .  673.978 
Combustion  ^lotive-Fluid  Gener- 
ator—Aru(dd 673,993 


PATENTS. 


817 


Pneumatic    Graiu-Loader— J.    E. 

Shepard 674,098 

Pneumatic  Shuttle   for  Looms- 
Baker 674.157 

Liquid  -  Elevatino-     Apparatus — 

Atkins ". 674,351 

Pneumatic  Despatch — ^L  Ander- 
son  674,373 

Pneumatic  Pian(j-Playiug  Device 

—Pain 674,426 

Pneumatic  Tire— W.  Covintree.  .674,436 

Seat    for   Air-Blast    Valves — AY. 

Fuller 674,460 

Air  Brake— A.  J.  Brishu 674,493 

Air  Brake— J.  R.  Ide 674,734 

G  o  V  e  r  u  o  r,    Air    Compressor — 

Christensen 674,808 

Direct -Ac  tin  g    Air   Pump — 

Wheeler.....' 674,819 

Air  Pump  for  Bicjcles — J.   Fur- 
bow 674,829 

Rock-Drilling  Machine — 'M.  Sinis- 
ter  674,881 

Regulator.     Pneumatic      Flue — 

Caffey 674,958 

Handle    for   Pneumatic    Tools — 

Kimman 674,971 

Air-^Iixer  and  Regulating  Valve 

— :Moore .^ 674,976 

Air    Brake     System — Cloves     ct 

Moves....'. .' 674,977 

Channelling  Machine — F.  E.  Beck- 
man 675,082 

Air-Brake  Coupling — ilcDougall 

675,100 

Pneumatic  Hoist — Rutherford.  .  .675,112 

River  Bed      Excavator  —  C.     H. 

Brown 675,124 

Pneumatic  Tire — Palmer  S:  Ber 

rodin 675,164 

Rock-Drilling  ^Machine — L.   Dur- 

kee 675,202 

Pressure  Rcirulator — J.  Roger.  .  .675,246 

Valve     for  ^Air    Brakes— E.    G. 

Shortt 675,251 

Rock  Drill— W.  S.  Bovd 675,319 

Air  Brake— J.  Guinan.' 675,328 

Pneumatic  Stacker — Mickelson.  .675,337 

Regulator,  Air  Compressor — Prell- 

witz 675,340 

Tunnelling  Device — MacHarg.. .  .675,355 

Action  for  ^lusical  Instruments^ 

Davis 675,468 


Rock  Drill— C.  T.  Litchlield 675,490 

Motor— C.  J.  Polock 675,497 

Valve,  Pneumatic  Hoist — Ruther- 
ford  675,528 

Valve-Gear,  Gas  Engine — G.  An- 
derson   675,581 

Pneumatic     Bench-Lifl — Doebler 

<k  Cooper 675,652 

Air  Brush— C.  Phillips 675,840 

Power  Transmitter — A.  Benson.  .675,849 

Air  Brake— C.  A.  Ball 675,870 

Portable  Pneumatic  Riveter — Car- 
lisle  675,880 

Pneumatic        Door-Check — Pere- 
grine  675,903 

Gas  and  Air  Heater  for  Buincrs  — 

Seifert 675,981 

Stoi^-Valve    for   Pneumatic  Tires 

— L.  Way 675,990 

Separator     for    Hydraulic    Com- 
pressor— ^  Webber 676,016 

Air  Brake— AVisner  S:  Elv 676,019 

Air  Separator— C.  II.  Lane 676,041 

Pneumatic  Tool — J.  J.  Tynan. .  ..676,055 
Compressino;  or  Exhausting  Fluids 

— Reavell    676,080 

Compressed-Air  SpraA'er — F.  Rip- 
ley  ". 676,204 

H  V  d  r  a  u  1  i  c   Air   Compressor — 

Mitchell 676.266 

Spring  Air-Gun — A.  Shoenhut.  ..676,279 
Pneumatic  Sheet-Feeding  Appa- 
ratus— Weiss  et  al 676,291 

Air   Compressor    and    Explosive 

Motor— Biasse 676,349 

Pneumatic  Tire— M.  A.  Heath.  .  .676,395 
Air  Brake — ]Malliuckrooz  it   Sau- 

vage 676,398 

Valve     for     Pneumatic     Tires — 

Spencer 676.400 

Air  Compressor — Textorius 676,401 

P  n  e  <i  m  a  t  i  c     Straw  -  Stacker — 

Wriaht 676.483 

Air  Brake— W.  H.  Sauvage 676,850 

Air  Brake— W.  H.  Sauvage 676,851 

Air  Brake— AV.  H.  Sauvage 676,852 

Pneumatic  Railwaj^  Brake— Brug- 

geman 676,871 

Hoist— AV.  F.  Barrett 676.931 

Caisson— AV.  II.  McFadden 676,993 

Rotating  Pump  or  Compressor — 

Dow 677,122 

Pneumatic  Tire— Tillinghast 677,290 


INDEX. 


Air  absorbed  by  water,  32 

absolute   temperature  and  its  zero, 

125 
brake,  598-608 

compressor,  287 
blast,  629 

paiutiug,  647-653 
bottle,  310 
brush,  616 
compressoi's,  271-290 

Clavtou,  317-324 

Curtiss,  354-360 

American  Steam  Pump  Co.,  380 

E.  P.  Allis  Co.,  350 

De  Auria,  383 

electric,  319,  385 

Guild  &  Garrison,  325-327 

gasoline,  404-407 

Ingersoll  -  Sergeant    Drill    Co., 
293-307 

four  stage,  304-307 

kerosene,  407 

Knowles,  328-335 

McKiernon,  353 

Merrill,  353 

N.  Y.  Air  Compressor  Co.,  361- 
365 

Nordberg,  391-403 

Norwalk,  339-349 

Rand  Drill  Co.,  369-379 

Phila.  Engineering  Works,  383 

Sedgwick'Fisher,  "391 

Still well-Bierce  &  S.-V.  Co.,  386 

St.  Louis  Steam  Engine  Co.,  381 

Laidlnw  D.  G.  Co.,  311-316 

submarine,  625 
compression,  low  pressure,  107 

isothermal,  116 

two  stage,  178-181 
compressor  governors,  320,  324,  349 

work,  167 
drills,  479-496 

densit}'  and  dry,  in  water,  31,  32 
drying  processes,  70 
and  vapor  (Table),  34,  35 
and  gasoline  braziers,  109 
in  motion  and  force,  43-45 
flow  in  pipes,  216-222 

into  vacuum,  87 
for  rock  drills,  417-436 
flow  from  orifices,  91 


Air,  gold  separator,  110 

guns,  696-699 

lock  system,  668 

liquid,  787 

lift  pump,  712-729 

loses  by  transmission,  223 
efficiency,  716 
hammers,  447—471 

nozzle,  type,  92 

physical  properties,  31-40 

plant  in  Paris,  243 

power  transmission,  213 

pressure  cards,  Corliss  engine,  253, 
254 
pump,  728 

pressures  below  atmospheric  press- 
ure, 51-69 

pyrometer,  559 

signal  equipment,  605 

signals,  593-595 

storage,  308-311 

specific  heat,  123 

vacuum  pumps,  51-53 

to  run  hoisting  engines,  pumps  and 
motors,  260-266 

transmission  tables,  319-331 

valves,  395,  357,  373 
Action  of  duplex  air  compressor,  385 
Actual  work  of  the  compressor,  165 
Adiabatic  card  of  work,  169 

compression  and  expansion,  135 
x\eration  of  water,  739 
Aging  of  liquors,  744 
Allen  dense  air  machine,  758 
Anemometers,  45-47 
Atmosphere,  height,  33,  33 
Ammunition  lift,  701 
Automatic  switch,  726 
Automobile  reheater,  233 
Auxiliary  valve,  418 


B 

Badger  rock  drill,  431 

Balfand  nozzle,  108 

Baggage  handler,  595 

Barometer,  ]iressures,  water  boils,  38 

Bar  channelling,  423 

Basket-makinsr,  615 

Bell  rin<,n'r.  609 

Belt  compressors,  296,  299,  317,  322,  355 

Bessemer  converter,  663 


INDEX. 


819 


Blowers,  types,  107 
Blast,  ail-,  «29 

sand,  680 

furuace,  663 
Blasting  coal,  667 
Blowing  engines,  350,  351 
Beyer  drill. "488-486 

hammer,  456,  457 
Brazing  apparatus,  109 

C 

Caisson  disease,  777 

sinking,  663-675 
Card  of  compressor  and  motor  work,  244 
of  slide  valve  air  engine,  245 
of  two-stage  compressor.  179 
of  three-stage  compression,  186 
of  four-stage  compression.  189 
Cards  of  Corliss  air  engine,  258,  254 
Caloric,  122 
Carriers,  tube,  681 
Carpet-cleaning,  654-659 
Caloric  engine,  284-239 
Coal  cutters.  428-425 
Chicago  rock  drill.  427 

pneumatic  drill,  400 
Clearance  table  for  motors,  201 
Coefficients  of  air  velocity.  98 
Compound   air    compressors,    290,    340, 
343,  347.  353,  359,  373 

lift,  721 
Compressed  air  hygiene.  775 

in  blast  furnace.  663 

for  blowing  glass,  110 

for  blasting  coal,  667 

for  hoisting  engines,  260 

in  mining,  417 

cars,  574^585 

haulage,  587 

on  railways,  578-586 

in  rolling-mill,  665 

in  ship-building,  492-496 

storage,  309.  310 

pumps,  730-787 

refrigeration,  748 

indicator  card,  155 

tables,  144-151 

f(n-  raising  water,  711-737 

in  warfare.  695 
Compressor  elliciencies  at  altitudes,  258 
Combustion  in  cylinders,  408 
Condensation  by  compression  and  cool- 
ing, 89 
Condenser  air  pumps,  56-58 
Contents  of  cylinders,  cubic  feet.  259 
Cooling  water  bv  air  expansion,  770 
Corliss  type.  303,  862,  874,  382,  892-398 
Cold  rooms,  764 
Cost  of  comjiressing  air.  587 

of  reheating  air.  282 
Cross   compound   air  compressors,   301, 

314,  315.  373 
Curves,  adiabatic.  140.  141 
Cyanide  and  air  gold  process,  742 


D 

Darlington  hydraulic  air  compressor,  282 
Den.se  air  refrigeration,  760 
Dewar  apparatus,  797 
Diagram,    isothermal    compression    and 
expansion,  116 

adiabatic    compression    and  expan- 
sion, 187 

combination  curves,  139 

of  air  expansion,  765 

of  three-stage  compression,  187 

of  four-stage  compression,  188 
Direct-acting  compressors,  830,  353,  380 

pressure  pumping,  724^726 
Diving  armor,  628 
Drills,  air,  479-495,  521 
Driven-well  system,  784 
Dry-placer  mining,  110 
Drying  in  vacuo,  64-72 
Dumping  cars,  597 
Dubois  &  Francois  compressor,  282 
Duplex  air  lift,  721-725 

compressor,  action,  285,  289 

compressors,  800,  303,  312,  816.  320, 
838-335,  850,  351,  862-864,  871 

Pelton  wheel  compressor,  298 

vei-tical  belt  compressors.  355-858 
Dusting  bj'  compressed  air,  653-656 
Dust  ti'lter,  654 
Dynamo  run  by  windmill,  105 

E 
Edison  reheater,  225 
Efficiency  of  air  lift,  716 

of  Grass  Valley  plant,  251,  252 

of  motors,  246,  247 

of  compressors,  high  altitudes.  257 
Electric  lighting  by  wind  power,  105 

air  compressor.  319 

meter,  563 
Endless  chain  in  air  pumping,  786 
Engines,  free  air  to  run,  260 
Energy  in  tube  transmission,  684 
English  tube  sj'stem,  682 
Engraving,  air,  644 
Equations  of  compression.  144 
Ericsson  hot-air  engine.  285,  286 
Expansion,  card  computation,  200 
of  work,  197 

formulas.  198,  199 

of  compressed  air  and  work  of  mo- 
tor, 197-209 

mean  pressure,  199 

temperatures,  198 

work  and  fornudas,  206-208 
Explosions  in  cylinders.  408 
Evaporation  by  air  (Tables),  47,  48 
Evaporators.  J.  Oats  &  Son,  83,  84 

Lillie.  81,  82 

Yaryan,  77-79 


Files,  sharpening,  645 
Filter  hood,  654 


820 


INDEX. 


First  law  of  thermodj'namics,  122 
Flow  of  fonipressod  air  in  ]iipes,  216-222 
Food  products,  drviuii-,  04-()9 
Foot- pound  work  of  coinprcssion,  170-171 
of   multiple    compression,    191, 
192 
Fog  signals,  617 
Formulas  for  air  tables,  218 

expansion  and  work,  198,  199 
air  velocity,  93 
isothermal,  118 

for  ratios  of  expansion,  203,  204 
thermodynamic,   128,   129,  139,  142, 

143,  170,  171,  172 
for  multiple  compression,  191-193 
work  of  expansion,  206-208 
for  air  flow  in  pipes,  216,  217 
Four-stage  air  compression,  187-193 

compressors,  302,  304,  306,  307 
Free  air  to  run  drills,  426 

to  run  engines,  pumps  and  mo- 
tors, 260,  266 
Friction  loss  of  air  pressure  in  pipes,  222 
Frizell  h^-draulic  air  compressor,  272 

G 

Gasoline  and  air  torch  light.  108 

.soldering  and  brazing,  109 
air  compressors,  404-407 
Gas  engine  air  compressor,  361 
Gay  Lussac's  law,  121 
Gold  mining  by  air  pressure,  110 
Governors,  air  "pressure,  321,  324,  349,  396 
Grain  ventilation  bj^  air  pressure,  110 
Graydon  gun,  699 

H 

Haesler  pneumatic  drill,  480 

Hammers,  air,  447,  499,  507,  508,  511 

Pland  air  compressors,  390 

Hargrave  kite,  100 

Hisrii  pressure  compression  types,  290, 

304.  377-379 
Hartford  air  compressor,  280 
Heat  a  mechanical  quantity,  122 
Hoisting  engines,  air  required,  260 
Hoists,  air,  533-553 

Horse  power  for  compressing  air,  181,  192 
Hold -on,  462,  511 
Hot-air  engines,  234-239 
Hydraulic  air  compressors,  271-282 

motor,  248.252 
plant.  Grass  Valley,  Cal.,  248-252 

Iron  Mountain,  Mich..  252-254 
Hygiene  of  compressed  air,  775 


Ice  machine.  Gorrie,  752 
Impact  or  force  of  percussion,  437 
Imperial  type,  compressor.  375 
Indicator  card.  the.  155-159 

steam  and  air.  160 
Indicator  cards,  computation.  200 

hot  air  engine,  239 


Indicator  cards,   multiple  compression, 

186,  189 
Ignition  in  cylinders  and  receivers,  410 
Ingersoll-Sergeant  rock  diills,  419-423 

coal  cutter,  421,  425 
Injector,  air,  630 
Intercoolinii:  and  intercoolers,  182,   185, 

340,  403,^413 
Interlocking  signals,  594 
Isothermal  card  of  work,  167 
compiession  of  air,  115 
diagram,  116 

J 
Jacks,  air,  550,  551 
Jet  compressor,  109 
conden.sers,  57,  58 


Kalsomining  by  air  jet,  647 
Kerosene  air  compressor,  407 

in  air  cylinder,  409 
Kites  and  their  work,  99-102 

L 
Leyner  rock  drill,  432 
Lift,  store  service,  686 
Linde  li(juid-air  apparatus,  793,  794 
Liquid  air,  787-802 
Liquid-air  plant,  798 
Little  Giant  drills,  481,  482 
hammers,  452—454 
Locomotive  bell  ringer,  609 
Locomotives,  589-592 

Baldwin  type,  589 

Porter  type,  592 
Log  flipper,  615 

nigger,  116 
Losses  in  air  pressure  by  transmission, 232 

31 

Mean  pressure  card,  159 
table,  149 

Mechanical  efficiencies,  190 
equivalents,  123.  124 

i\Iekarski  reheater,  231 

^lercurial  air  pump,  54 

]Meter  measurement,  compressed  air,  266 
268 

3Ioisture  in  air  (Tables).  35.  36 

Motor,  compressed  air  and  work,  197 
efficiencies:  Paris.  246.  247 
work ;  Kennedy  report.  244 

Motors,  air  requiied  to  run,  265 

McKiernan  rock  drill.  429 

Mountain  pressures :  water  boils,  38 

Moulding  machine.  516 

Monitor  Terror,  air  work.  700 

Multiple-stage  air  lift.  721.  722 

Multi-stage  air  compression,  177-181 

Xozzle.  air  tvpe.  92 
dusting. "653.  654 
paint  spraj',  648 


INDEX. 


82  1 


O 

Orifices,  flow  of  air  Uirougli,  91 


Pelton  wheel  air  compressors,  248,  290, 

841,  342 
Pistou  air  drills,  505-510 

inlet  and  valve,  295 
Petroleum  bui'ner,  647 
Phceuix  drill.  488 
Power  of  air,  487 

plant;  Paris,  214 
Pohle  air  lift,  712,  713 
Point  of  stroke  (Table),  149 
Pneumatic  tools,  447-551 

drills,  479-495,  521 

i>ims,  (596-099 

hammers,  447-499,  507 

hoists,  533-553 

jacks,  550,  551 

nozzles,  653,  654 

punch,  555-557 

painting,  647-652 

saw,  551 

sheep  shearing,  613 

stay-bolt  cutters,  549 

telegraph,  598 

tools  in  shij)  Iniilding,  4G6-471 
construction,  472-478 

postal  tube  service,  676 

welding  machine,  517 
Pressure  of  air  at  sea  level,  124 

and  heat  dia<rram,  139 

of  the  Avind  "(Table),  44 
Preservation  of  wood  by  vacuum,  68 
Pumping  by  wind  power,  104 
Pumps,  air  required  to  run,  261,  264 
Purifying  water  by  air,  74() 
Pyrometry,  555-5(39 

Q 

Q.  and  C.  hanuners,  450,  451,  499 

R 

Railway  gate,  596 
Raising- water,  711-737 
Rammers,  sand,  512,  513 
Rami  rock  drills,  434-436 

reheater,  229,  230 
Ratio  of  expansion,  126 
Ratios  of  compression  (Table),  149 
Reducing  valve,  583 
Refrigeration,  747-770 
Regulators,  air  pressure,  349,  396 
Reheating  of  air  and  its  work,  225-233 
Rider  hot-air  engine.  237,  239 
Riveter,  stationary,  505 

voke,  472,  475,  503,  504     ' 
Rock  drills,  417-436 
Rock-drill  reheater,  226 
Rolling-mill,  665 
Rotary  drill,  488 


S 

Salt -making  in  vacuo,  72-75 
Sand  brush,  515 

sifter,  515 

blast,  630-641 

blast  cleaning,  046 
Sculpture  and  stone  cutting,  463,  464 
Sergeant  reheater,  227,  228 
Sawmill,  compressed  air  in,  615 
Sewage  lifting,  737 
Simple  reheater,  225 
Sheep  shearing,  613 
Signals,  air,  593-595 
Siren  or  fog-horn,  618 
Siphon,  85 

pressure  gauge,  47 
Stage  compression,  178,  193 
two  stage,  178,  181 
three  stage,  186,  187 
four  stage,  187,  193 
Stay-bolt  cutters,  549 
Steering  apparatus,  706 
Steam  and  air  card,  160 
Store  service,  tube,  687 
Stone  hammers,  502 
Straight-line  air  compressor,  287 
Submarine  exploration,  621-626 
Sunken  vessels,  raising,  619,  620 


Table  I.  Air  absorbed  by  water,  32 

II.  Air    and    vapor,    volumes    and 
weight,  35 

III.  Moisture  in  air  at  various  press- 
ures, 36 

IV.  Weight  of  vapor  per  cubic  foot, 
37 

V.  Height  of  barometer-boiling  tem- 
perature, 38 

VI.  Water    condensed    from    com- 
]iressed  air,  40 

VII.  Wind  velocity  and  pressTire,  44 

VIII.  Evaporation  of  water  bv  air, 
48 

IX.  Evaporation  in  vacuo,  59 

X.  Velocitj^  of  air  from  orifices,  91 

XI.  Velocity  and  air  coefficients,  94 

XII.  Flow  in  cubic  feet  from  orifices, 
94,  95 

XIII.  Windmill  power,  104 

XIV.  Specific  heat  of  air,  124 

XV.  Volume,  pressure,  and  density. 
Air,  129 

XVI.  Pressures,   temperatures,  and 
volumes,  145 

XVII.  Gauge  pressures,  ratios,  point 
of  stroke,"  149 

XVIII.  IVIean  pressure  in  cylinder 
and  delivery,  166 

XIX.  Foot-pound     work    of    com- 
pression, 171 

XX    Power  lost  in  compression,  180 
XXI.   Horse     power;     multi-stage 
compression,  192 


822 


INDEX. 


Table  XXII.  Excess  of  cut-off  for  clear- 
ance, 201 

XXIII.  Ratios  of  pressures  and  tem- 
perature, 202 

XXIV.  Mean  and  terminal  pressures 
in  motor,  205 

XXV.  Pipe   areas    and   coefficients, 
217 

XXVI.  Gauge    presstires,     weight, 
^^,  218" 

XXVII.  Air  transmission, 45-pounds 
gauge,  219 

XXVill.     Air       transmission,     60- 
pounds  gauge,  220 

XXIX.  Air  transmission,  75-pounds 
gauge,  220 

XXX.  Air   transmission,  90-pounds 
gauge,  221 

XXXi.   Air  transmission,  lO.j-pounds 

gauge,  221 
XXXil.    Loss    in    air    pressure    in 

pipes,  222 

XXXIII.  Compressor  efficiencies  at 
altitudes,  258 

XXXIV.  Contents  of  cylinders,  259 

XXXV.  Free  air  required  for  hoist- 
ing engines,  260 

XXXVI.  Free     air     required     for 
pumps  and  motors,  261 

XXXVII.  Free    air    required    for 
pamps,  "Weber,"  262 

XXXVIII.  Free    air    required    for 
pumping  water,  "Halsey,"  264 

XXXIX.  Free  air  required  per  I. 
H.  P.  "Weber,"  265 

XL.  Free  air  required  for  rock  drills 
"I.  S.  D.  Co."  426 

XLI.  Free    air   required    for   Rand 
rock  drills,  435 

XLI  I.  Factors  for  drills  at  elevation, 
436 
Tandem  Corliss  compressor,  289 
Tappet  valve,  418 

Taylor  hvdraulic  air  compressor,  273,  279 
Telegraph,  air,  598 
Temperature,  boiling,  at  altitudes,  38 

diagram,  139 

in  hot-air  engine.  237 
Terminal  air  pressure,  198 

valves,  689 
Terror,  mouitor,  700-707 
Thermodynamics,  121 
Thermal  "unit,  122 
Three-stage  aii'  compression,  186,  187 

compres.sors,  323,  345,  346,  400 
Tilden  hammer,  458 
Transmission  of  air  ])ower,  213 

air  tables,  219-221 

long  distance,  220 
Triple  valve,  599-601 
Tripler  liquid  air  apparatus,  796 
Trollev  car  air  brake,  607 
Trompe,  271 
Tube  transmission,  675-686 


Tube  well  air  lift,  723 

Two-stage  air  compression,  178-181 

lift  pump,  726 
Types  of  air  compressors,  283 

U 

Unloading  devices,  295,  297,  370,  393 
Utility  of  a  vacuum,  64-84 

V 
Vacuum  and  its  work,  51-84 

excavator,  85 

flow  of  air  into,  87 

process  for  salt,  72 

pumps,  52-69 
Valve,  reducing,  583 
Valves,  air  brake,  599-604 

compressor,  327,  357,  358,  359 
Velocity  and  pressure,  wind,  44 

of  the  wind  and  force,  104 
Venturi  nozzle,  92 

vacuum  pump,  53 
Vertical  air  compressors,  329,  355,  356, 
365,  381 

valve  cylinder,  295 
Volume  of  expansion  for  any  tempera- 
ture, 129,  130 
Vulcanizing  wood,  743 

W 

Wall  or  post  compressors,  317,  328 
Water  aeration,  739 

condensed  from  compressed  air,  40 

works,  717 
Weight  of  air,  124,  130 
Welding  machine,  517 
Windmill  and  its  work,  102 

for  electric  lighting,  105 
Wind  power.  99 

vclocitv  and  force,  43,  44 
Whitlaw  dnll,  485,  491 
"Whitewashing  by  air,  647 
Whistles,  air,  616 
Wood  vulcanizing,  743 
Work,  adiabatic  diagram,  169 

isothei'mal  diagram,  167 

of  expansion,  206-208 

foot  pounds  of  compression,  168-172 

foot  pound,  multi-compression,  191- 
193 

of  the  sand  blast,  633 

of  reheating,  225,  233 

of  the  compressor,  165,  167 


Yacht  and  launch  whistles,  616 

Yaryan  evaporator,  77 

Yoke  riveters,  472,  474,  503,  504 


Zalinski  gun,  696 

Zero  diagram  of  absolute  temperature, 
126 


msam^^m 


Quarry- 
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COAL 
CUTTERS 


THE 


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Air  Compressors 


ACTUATED    BY 


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i6  WARREN   ST.,   NEW  YORK 


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MANUFACTURED  EXCLUSIVELY  BY 


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i6  WARREN    ST.,   NEW^  YORK 


University  of  California 

SOUTHERN  REGIONAL  LIBRARY  FACILITY 

405  Hilgard  Avenue,  Los  Angeles,  CA  90024-1388 

Return  this  material  to  the  library 

from  which  it  was  borrowed. 


UC  SOUTHERN  REGIOIIAI  IIRRAR^  F 


STACK 

./fiL7J    * 


A     000  558  551     8 


